Thermoelectric generator system

ABSTRACT

A thermoelectric generator system according to the present disclosure includes first and second thermoelectric generator units, each including tubular thermoelectric generators. Each of the generators has a flow path defined by its inner peripheral surface, and generates electromotive force in an axial direction thereof based on a temperature difference between its inner and outer peripheral surfaces. Each unit further includes: a container housing the generators inside; and electrically conductive members providing electrical interconnection for the generators. The container has fluid inlet and outlet ports through which a fluid flows inside, and openings into which the generators are inserted. A buffer vessel is arranged between the first and second units, and has a first opening communicating with the flow paths of the generators in the first unit and a second opening communicating with the flow paths of the generators in the second unit.

This is a continuation of U.S. patent application Ser. No. 14/680,402,with a filing date of Apr. 7, 2015, which is a continuation ofInternational Application No. PCT/JP2014/001284, with an internationalfiling date of Mar. 7, 2014, which claims priority of Japanese PatentApplication No. 2013-048864, filed on Mar. 12, 2013, the contents ofwhich are hereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a thermoelectric generator systemincluding a plurality of thermoelectric generator units. The presentdisclosure also relates to a method of producing the thermoelectricgenerator system.

2. Description of the Related Art

A thermoelectric conversion element is an element which can converteither heat into electric power or electric power into heat. Athermoelectric conversion element made of a thermoelectric material thatexhibits the Seebeck effect can obtain thermal energy from a heat sourceat a relatively low temperature (of 200 degrees Celsius or less, forexample) and can convert the thermal energy into electric power. With athermoelectric generation technique based on such a thermoelectricconversion element, it is possible to collect and effectively utilizethermal energy which would conventionally have been dumped unused intothe ambient in the form of steam, hot water, exhaust gas, or the like.

A thermoelectric conversion element made of a thermoelectric materialwill be hereinafter referred to as a “thermoelectric generator”. Athermoelectric generator generally has a so-called “π structure” wherep- and n-type semiconductors, of which the carriers have mutuallydifferent electrical polarities, are combined together (see JapaneseLaid-Open Patent Publication No. 2013-016685, for example). In athermoelectric generator with the π structure, a p-type semiconductorand an n-type semiconductor are connected together electrically inseries together and thermally parallel with each other. In the πstructure, the direction of a temperature gradient and the direction ofelectric current flow are either mutually parallel or mutuallyantiparallel to each other. This makes it necessary to provide an outputterminal on the high-temperature heat source side or the low-temperatureheat source side. Consequently, to connect a plurality of suchthermoelectric generators, each having the π structure, electrically inseries together, a complicated wiring structure is required.

PCT International Application Publication No. 2008/056466 (which will behereinafter referred to as “Patent Document 1”) discloses athermoelectric generator including a stacked body of a bismuth layer anda layer of a different metal from bismuth between first and secondelectrodes that face each other. In the thermoelectric generatordisclosed in Patent Document 1, the planes of stacking are inclined withrespect to a line that connects the first and second electrodestogether. PCT International Application Publication No. 2012/014366(which will be hereinafter referred to as “Patent Document 2”), kanno etal., preprints from the 72^(nd) Symposium of the Japan Society ofApplied Physics, 30a-F-14 “A Tubular Electric Power Generator UsingOff-Diagonal Thermoelectric Effects” (2011), and A. Sakai et al.,International conference on thermoelectrics 2012 “Enhancement inperformance of the tubular thermoelectric generator (TTEG)” (2012)disclose tubular thermoelectric generators.

SUMMARY

Development of a practical thermoelectric generator system that usessuch thermoelectric generation technologies is awaited.

A thermoelectric generator system according to an implementation of thepresent disclosure includes a plurality of thermoelectric generatorunits including first and second thermoelectric generator units, each ofwhich includes a plurality of tubular thermoelectric generators. Each ofthe plurality of tubular thermoelectric generators has an outerperipheral surface, an inner peripheral surface and a flow path definedby the inner peripheral surface, and generates electromotive force in anaxial direction of each tubular thermoelectric generator based on adifference in temperature between the inner and outer peripheralsurfaces. Each of the first and second thermoelectric generator unitsfurther includes: a container housing the plurality of tubularthermoelectric generators inside, the container having fluid inlet andoutlet ports through which a fluid flows inside the container, and aplurality of openings into which the respective tubular thermoelectricgenerators are inserted; and a plurality of electrically conductivemembers providing electrical interconnection for the plurality oftubular thermoelectric generators. The thermoelectric generator systemfurther includes a buffer vessel which is arranged between the first andsecond thermoelectric generator units. The buffer vessel has a firstopening communicating with the respective flow paths of the plurality oftubular thermoelectric generators in the first thermoelectric generatorunit and a second opening communicating with the respective flow pathsof the plurality of tubular thermoelectric generators in the secondthermoelectric generator unit.

A thermoelectric generator system according to the present disclosurecontributes to increasing the practicality of thermoelectric powergeneration.

These general and specific aspects may be implemented using a system anda method, and any combination of systems and methods.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and Figures. The benefits and/oradvantages may be individually provided by the various embodiments andfeatures of the specification and drawings disclosure, and need not allbe provided in order to obtain one or more of the same.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional view of a thermoelectricgenerator 10.

FIG. 1B is a top view of the thermoelectric generator 10 shown in FIG.1A.

FIG. 2 schematically illustrates a situation where a high-temperatureheat source 120 is brought into contact with the upper surface 10 a ofthe thermoelectric generator 10 and a low-temperature heat source 140 isbrought into contact with its lower surface 10 b.

FIG. 3A is a perspective view illustrating an exemplary generalconfiguration for a tubular thermoelectric generator T which may be usedin an exemplary thermoelectric generator system according to the presentdisclosure.

FIG. 3B is a perspective view illustrating a general configuration foran exemplary thermoelectric generator unit 100 that a thermoelectricgenerator system according to the present disclosure has.

FIG. 4 is a block diagram illustrating an exemplary configuration forcreating a temperature difference between the outer and inner peripheralsurfaces of the tubular thermoelectric generator T.

FIG. 5 schematically illustrates how the tubular thermoelectricgenerators T1 to T10 may be electrically connected together.

FIG. 6A is a perspective view illustrating one of the tubularthermoelectric generators T (e.g., the tubular thermoelectric generatorT1 in this example) that the thermoelectric generator unit 100 has.

FIG. 6B schematically illustrates a cross section where the tubularthermoelectric generator T1 is cut along a plane which contains the axis(center axis) of the tubular thermoelectric generator T1.

FIG. 7A is a front view illustrating an implementation of athermoelectric generator unit that a thermoelectric generator systemaccording to the present disclosure has.

FIG. 7B illustrates one of the side surfaces of the thermoelectricgenerator unit 100 (a right side view in this case).

FIG. 8 schematically illustrates a portion of a cross section of thethermoelectric generator unit 100 as viewed on the plane M-M shown inFIG. 7B.

FIG. 9 schematically shows exemplary flow directions of the hot and coldheat transfer media introduced into the thermoelectric generator unit100.

FIG. 10 schematically illustrates a cross section of a portion of aplate 36 and the appearance of an electrically conductive member J1.

FIG. 11A is an exploded perspective view schematically illustrating thechannel C61 to house the electrically conductive member J1 and itsvicinity.

FIG. 11B is a perspective view schematically illustrating a portion ofthe sealing surface of the second plate portion 36 b (i.e., the surfacethat faces the first plate portion 36 a) associated with the openingsA61 and A62.

FIG. 12A is a perspective view illustrating an exemplary shape of theelectrically conductive ring member 56.

FIG. 12B is a perspective view illustrating another exemplary shape ofthe electrically conductive ring member 56.

FIG. 13A is a cross-sectional view schematically illustrating theelectrically conductive ring member 56 and tubular thermoelectricgenerator T1.

FIG. 13B is a cross-sectional view schematically illustrating a statewhere an end of the tubular thermoelectric generator T1 has beeninserted into the electrically conductive ring member 56.

FIG. 13C is a cross-sectional view schematically illustrating a statewhere an end of the tubular thermoelectric generator T1 has beeninserted into the electrically conductive ring member 56 andelectrically conductive member J1.

FIG. 14A is a cross-sectional view schematically illustrating theelectrically conductive ring member 56 and a portion of the electricallyconductive member J1.

FIG. 14B is a cross-sectional view schematically illustrating a statewhere the elastic portions 56 r of the electrically conductive ringmember 56 have been inserted into the through hole Jh1 of theelectrically conductive member J1.

FIG. 15 is a cross-sectional view illustrating an exemplary tubularthermoelectric generator T with a chamfered portion Cm at its end.

FIG. 16A schematically illustrates how electric current flows in tubularthermoelectric generators T which are electrically connected together inseries.

FIG. 16B schematically illustrates how electric current flows in tubularthermoelectric generators T which are electrically connected together inseries.

FIG. 17 schematically shows the directions in which electric currentflows through the two openings A61 and A62 and their surrounding region.

FIG. 18A is a perspective view illustrating an exemplary tubularthermoelectric generator, of which the electrodes have indicators oftheir polarity.

FIG. 18B is a perspective view illustrating another exemplary tubularthermoelectric generator, of which the electrodes have indicators oftheir polarity.

FIG. 19 illustrates the other side face of the thermoelectric generatorunit 100 shown in FIG. 7A (left side view).

FIG. 20 schematically illustrates a cross section of a portion of aplate 34 and the appearance of an electrically conductive member K1.

FIG. 21 is an exploded perspective view schematically illustrating thechannel C41 to house the electrically conductive member K1 and itsvicinity.

FIG. 22 is a cross-sectional view schematically illustrating anexemplary structure for separating the medium which flows in contactwith the outer peripheral surfaces of the tubular thermoelectricgenerators T from the medium which flows in contact with the innerperipheral surface of each of the tubular thermoelectric generators T1to T10 so as to prevent those media from mixing together.

FIG. 23A is a cross-sectional view schematically illustrating anotherexemplary structure for separating the hot and cold heat transfer mediafrom each other and electrically connecting the tubular thermoelectricgenerator and the electrically conductive member together.

FIG. 23B is a cross-sectional view schematically illustrating stillanother exemplary structure for separating the hot and cold heattransfer media from each other and electrically connecting the tubularthermoelectric generator and the electrically conductive membertogether.

FIG. 24A illustrates an embodiment of a thermoelectric generator systemaccording to the present disclosure.

FIG. 24B is a cross-sectional view of the system as viewed on the planeB-B shown in FIG. 24A.

FIG. 24C is a perspective view illustrating an exemplary configurationfor a buffer vessel that the thermoelectric generator system shown inFIG. 24A has.

FIG. 25A illustrates another embodiment of a thermoelectric generatorsystem according to the present disclosure.

FIG. 25B is a cross-sectional view of the system as viewed on the planeB-B shown in FIG. 25A.

FIG. 25C is a cross-sectional view of the system as viewed on the planeC-C shown in FIG. 25A.

FIG. 26A illustrates still another embodiment of a thermoelectricgenerator system according to the present disclosure.

FIG. 26B is a cross-sectional view of the system as viewed on the planeB-B shown in FIG. 26A.

FIG. 27A illustrates yet another embodiment of a thermoelectricgenerator system according to the present disclosure.

FIG. 27B is a cross-sectional view of the system as viewed on the planeB-B shown in FIG. 27A.

FIG. 28A illustrates yet another embodiment of a thermoelectricgenerator system according to the present disclosure.

FIG. 28B is a cross-sectional view of the system as viewed on the planeB-B shown in FIG. 28A.

FIG. 29 illustrates yet another embodiment of a thermoelectric generatorsystem according to the present disclosure.

FIG. 30 is a block diagram illustrating an exemplary configuration of anelectric circuit that the thermoelectric generator system according tothe present disclosure may include.

FIG. 31 is a block diagram illustrating an exemplary configuration foranother embodiment in which a thermoelectric generator system accordingto the present disclosure may be used.

DETAILED DESCRIPTION

A thermoelectric generator system according to a non-limiting exemplaryimplementation of the present disclosure includes a plurality ofthermoelectric generator units including first and second thermoelectricgenerator units, each of which includes a plurality of tubularthermoelectric generators. Each of the tubular thermoelectric generatorshas an outer peripheral surface, an inner peripheral surface and a flowpath defined by the inner peripheral surface, and is configured togenerate electromotive force in an axial direction of each tubularthermoelectric generator based on a difference in temperature betweenthe inner and outer peripheral surfaces.

Each of the first and second thermoelectric generator units furtherincludes: a container housing the tubular thermoelectric generatorsinside; and a plurality of electrically conductive members providingelectrical interconnection for the tubular thermoelectric generators.The container has fluid inlet and outlet ports through which a fluidflows inside the container, and a plurality of openings into which therespective tubular thermoelectric generators are inserted.

The thermoelectric generator system according to this implementationfurther includes a buffer vessel which is arranged between the first andsecond thermoelectric generator units. The buffer vessel has first andsecond openings. The first opening communicates with the respective flowpaths of the tubular thermoelectric generators in the firstthermoelectric generator unit, and the second opening communicates withthe respective flow paths of the tubular thermoelectric generators inthe second thermoelectric generator unit.

<Basic Configuration and Principle of Operation of ThermoelectricGenerator>

Before embodiments of a thermoelectric generator system according to thepresent disclosure are described, the basic configuration and principleof operation of a thermoelectric generator for use in eachthermoelectric generator unit that the thermoelectric generator systemhas will be described. As will be described later, in a thermoelectricgenerator system according to the present disclosure, a tubularthermoelectric generator is used. However, the principle of operation ofsuch a tubular thermoelectric generator can also be understood moreeasily through description of the principle of operation of athermoelectric generator in a simpler shape.

First of all, look at FIGS. 1A and 1B. FIG. 1A is a schematiccross-sectional view of a thermoelectric generator 10 with a generallyrectangular parallelepiped shape, and FIG. 1B is a top view of thethermoelectric generator 10. For reference sake, X-, Y- and Z-axis thatintersect with each other at right angles are shown in FIGS. 1A and 1B.The thermoelectric generator 10 shown in FIGS. 1A and 1B includes astacked body with a structure in which multiple metal layers andthermoelectric material layers 22 are alternately stacked one upon theother so that their planes of stacking are inclined. Although thestacked body is supposed to have a rectangular parallelepiped shape inthis example, the principle of operation will be the same even if thestacked body has any other shape.

In the thermoelectric generator 10 shown in FIGS. 1A and 1B, first andsecond electrodes E1 and E2 are arranged so as to sandwich the stackedbody horizontally between them. In the cross section shown in FIG. 1A,the planes of stacking define an angle of inclination θ (where 0<θ<πradians) with respect to the Z-axis direction. The angle of inclinationθ will be hereinafter simply referred to as an “inclination angle”.

In the thermoelectric generator 10 with such a configuration, when atemperature difference is created between its upper surface 10 a and itslower surface 10 b, the heat will be transferred preferentially throughthe metal layers 20 with higher thermal conductivity than thethermoelectric material layers 22. Thus, a Z-axis direction component isproduced in the temperature gradient of each of those thermoelectricmaterial layers 22. As a result, electromotive force occurs in theZ-axis direction in each thermoelectric material layer 22 due to theSeebeck effect, and eventually the electromotive forces are superposedone upon the other in series inside this stacked body. Consequently, asignificant potential difference is created as a whole between the firstand second electrodes E1 and E2. A thermoelectric generator includingthe stacked body shown in FIGS. 1A and 1B is disclosed in PCTInternational Application Publication No. 2008/056466 (Patent Document1), the entire disclosure of which is hereby incorporated by reference.

FIG. 2 schematically illustrates a situation where a high-temperatureheat source 120 is brought into contact with the upper surface 10 a ofthe thermoelectric generator 10 and a low-temperature heat source 140 isbrought into contact with its lower surface 10 b. In such a situation,heat Q flows from the high-temperature heat source 120 toward thelow-temperature heat source 140 through the thermoelectric generator 10,and electric power P can be extracted from the thermoelectric generator10 through the first and second electrodes E1 and E2. From a macroscopicpoint of view, in this thermoelectric generator 10, the direction oftemperature gradient (Y-axis direction) and the direction of theelectric current (Z-axis direction) intersect with each other at rightangles. That is why there is no need to create a temperature differencebetween the two electrodes E1 and E2, through which the electric poweris extracted. FIG. 2 schematically illustrates an example in which theelectric power P flows from the left toward the right on the paper.However, this is only an example. For example, if the kind of thethermoelectric material used is changed, the electric power P may flowin the opposite direction from the one shown in FIG. 2.

Although the stacked body of the thermoelectric generator 10 is supposedto have a rectangular parallelepiped shape in the example describedabove for the sake of simplicity, a thermoelectric generator, of whichthe stacked body has a tubular shape, will be used in the embodiments tobe described below. A thermoelectric generator in such a tubular shapewill be hereinafter referred to as a “tubular thermoelectric generator”or “thermoelectric generation tube”. It should be noted that in thepresent specification, the term “tube” is interchangeably used with theterm “pipe”, and is to be interpreted to encompass both a “tube” and a“pipe”.

<Outline of Thermoelectric Generator Unit>

Next, a thermoelectric generator unit of the thermoelectric generatorsystem according to the present disclosure will be outlined.

First of all, look at FIGS. 3A and 3B. FIG. 3A is a perspective viewillustrating an exemplary tubular thermoelectric generator T. Thetubular thermoelectric generator T includes a tube body Tb in whichmultiple metal layers 20 and thermoelectric material layers 22 with athrough hole at their center are alternately stacked one upon the otherso as to be inclined and a pair of electrodes E1 and E2. A method ofmaking such a tubular thermoelectric generator T is disclosed in PatentDocument 2, for example. According to the method disclosed in PatentDocument 2, multiple metallic cups, each having a hole at the bottom,and multiple thermoelectric material cups, each also having a hole atthe bottom, are alternately stacked one upon the other and subjected toa plasma sintering process in such a state, thereby binding themtogether. The entire disclosure of PCT International ApplicationPublication No. 2012/014366 is hereby incorporated by reference.

The tubular thermoelectric generator T shown in FIG. 3A may be connectedto a conduit so that a hot heat transfer medium flows through a flowpath defined by its inner peripheral surface (which will sometimes bereferred to as an “internal flow path” hereinbelow). In that case, theouter peripheral surface of the tubular thermoelectric generator T maybe brought into contact with a cold heat transfer medium. In thismanner, a temperature difference is created between the inner and outerperipheral surfaces of the tubular thermoelectric generator T, therebygenerating a potential difference between the pair of electrodes E1 andE2. As a result, the electric power generated can be extracted.

It should be noted that although these heat transfer media will bereferred to herein as “hot” and “cold” heat transfer media, these terms“hot” and “cold” actually do not refer to specific absolute temperaturelevels of those media but just mean that there is a relative temperaturedifference between those media. Also, the “medium” is typically a gas, aliquid or a fluid that is a mixture of a gas and a liquid. However, the“medium” may contain solid, e.g., powder, which is dispersed within afluid. Hereinbelow, the hot heat transfer medium and the cold heattransfer medium will sometimes be simply referred to as “the hot medium”and “the cold medium”, respectively.

The shape of the tubular thermoelectric generator T may be anythingtubular, without being limited to cylindrical. In other words, when thetubular thermoelectric generator T is cut along a plane which isperpendicular to the axis of the tubular thermoelectric generator T, theresultant shapes created by sections of the “outer peripheral surface”and the “inner peripheral surface” do not need to be circles, but may beany closed curves, e.g., ellipses or polygons. Although the axis of thetubular thermoelectric generator T is typically linear, it is notlimited to being linear. These can be seen easily from the principle ofthermoelectric generation that has already been described with referenceto FIGS. 1A, 1B and 2.

FIG. 3B is a perspective view illustrating a general configuration foran exemplary thermoelectric generator unit 100 that a thermoelectricgenerator system according to the present disclosure has. Thethermoelectric generator unit 100 shown in FIG. 3B includes a pluralityof tubular thermoelectric generators T, a container 30 which housesthese tubular thermoelectric generators T inside, and a plurality ofelectrically conductive members J to electrically connect these tubularthermoelectric generators T together. In the example illustrated in FIG.3B, ten tubular thermoelectric generators T1 to T10 are housed insidethe container 30. Those ten tubular thermoelectric generators T1 to T10are typically arranged substantially parallel to each other but may alsobe arranged in any other pattern.

Each of these tubular thermoelectric generators T1 to T10 has an outerperipheral surface, an inner peripheral surface, and an internal flowpath defined by the inner peripheral surface as described above. Each ofthese tubular thermoelectric generators T1 to T10 is configured togenerate electromotive force along its axis based on a difference intemperature created between the inner and outer peripheral surfaces.That is to say, by creating a temperature difference between the outerand inner peripheral surfaces in each of those tubular thermoelectricgenerators T1 to T10, electric power generated can be extracted from thetubular thermoelectric generators T1 to T10. For example, by bringing ahot medium and a cold medium into contact with the internal flow pathand the outer peripheral surface, respectively, in each of the tubularthermoelectric generators T1 to T10, electric power generated can beextracted from the tubular thermoelectric generators T1 to T10.Conversely, a cold medium and a hot medium may be brought into contactwith the inner and outer peripheral surfaces, respectively, in each ofthe tubular thermoelectric generators T1 to T10.

In the example illustrated in FIG. 3B, the medium to be brought intocontact with the outer peripheral surfaces of the tubular thermoelectricgenerators T1 to T10 inside the container 30 and the medium to bebrought into contact with the inner peripheral surface of each tubularthermoelectric generator T1 to T10 in the internal flow path of therespective tubular thermoelectric generator are supplied throughdifferent conduits (not shown), thus being isolated so as not tointermix.

FIG. 4 is a block diagram illustrating an exemplary configuration forintroducing a temperature difference between the outer and innerperipheral surfaces of the tubular thermoelectric generator T. In FIG.4, the dotted arrow H schematically indicates the flow of a hot mediumand the solid arrow L schematically indicates the flow of a cold medium.In the example illustrated in FIG. 4, the hot and cold media arecirculated by pumps P1 and P2, respectively. For example, the hot mediummay be supplied to the internal flow path in each of the tubularthermoelectric generators T1 to T10 and the cold medium may be suppliedinto the container 30. Although not shown in FIG. 4, heat is suppliedfrom a high-temperature heat source (such as a heat exchanger, notshown) to the hot medium and heat is supplied from the cold medium to alow-temperature heat source (not shown, either). As the high-temperatureheat source, steam, hot water and exhaust gas at relatively lowtemperatures (of 200 degrees Celsius or less, for example) which havebeen dumped unused into the ambient can be used. Naturally, heat sourcesat even higher temperatures may also be used.

In the example illustrated in FIG. 4, the hot and cold media aresupposed to be circulated by the pumps P1 and P2, respectively. However,this is only an example of a thermoelectric generator system accordingto the present disclosure. Alternatively, one or both of the hot andcold media may be dumped from their heat source into the ambient withoutforming a circulating system. For example, high-temperature hot springwater that has sprung from the ground may be supplied as the hot mediumto the thermoelectric generator unit 100, and when its temperaturelowers, the hot spring water may be used for any purpose other thanpower generation or just discharged. The same can be said about the coldmedium. That is to say, phreatic water, river water or seawater may bepumped up and supplied to the thermoelectric generator unit 100. Afterany of these kinds of water has been used as the cold medium, itstemperature may be lowered to an appropriate level as needed and thenthe water may be either poured back to its original source or justdischarged to the ambient.

Now look at FIG. 3B again. In the thermoelectric generator unit 100according to the present disclosure, a plurality of tubularthermoelectric generators T are electrically connected together via theelectrically conductive members J. In the example illustrated in FIG.3B, each pair of tubular thermoelectric generators T arranged adjacentto each other are connected together via their associated electricallyconductive member J. As a result, these tubular thermoelectricgenerators T are electrically connected together in series as a whole.For example, the respective right ends of two tubular thermoelectricgenerators T3 and T4 which are illustrated as front ones in FIG. 3B areconnected together with an electrically conductive member J3. On theother hand, the respective left ends of these two tubular thermoelectricgenerators T3 and T4 are connected to two other tubular thermoelectricgenerators T2 and T5 via electrically conductive members J2 and J4,respectively.

FIG. 5 schematically illustrates how those tubular thermoelectricgenerators T1 to T10 may be electrically connected together. As shown inFIG. 5, each of the electrically conductive members J1 to J9electrically connects its associated two tubular thermoelectricgenerators together. That is to say, the electrically conductive membersJ1 to J9 are arranged to electrically connect these tubularthermoelectric generators T1 to T10 in series together as a whole. Inthis example, the circuit comprised of the tubular thermoelectricgenerators T1 to T10 and the electrically conductive members J1 to J9 isa traversable one. However, this circuit may also include some tubularthermoelectric generators which are connected in parallel, and it is notessential that the circuit be traversable.

In the example illustrated in FIG. 5, an electric current may flow fromthe tubular thermoelectric generator T1 to the tubular thermoelectricgenerator T10, for example. However, the electric current may also flowfrom the tubular thermoelectric generator T10 to the tubularthermoelectric generator T1. The direction of this electric current isdetermined by the kind of a thermoelectric material used to make thetubular thermoelectric generator T, the direction of flow of heatgenerated between the inner and outer peripheral surfaces of the tubularthermoelectric generator T, and the direction of inclination of theplanes of stacking in the tubular thermoelectric generator T, forexample. The connection of the tubular thermoelectric generators T1 toT10 is determined so that electromotive forces occurring in therespective tubular thermoelectric generators T1 to T10 do not cancel oneanother, but are superposed.

It should be noted that the direction in which the electric currentflows through the tubular thermoelectric generators T1 to T10 hasnothing to do with the direction in which the medium (i.e., either thehot medium or the cold medium) flows through the internal flow path ofthe tubular thermoelectric generators T1 to T10. For instance, in theexample illustrated in FIG. 5, the medium going through the internalflow path may flow from the left toward the right on the paper in eachand every one of the tubular thermoelectric generators T1 to T10.

<Detailed Configuration of Tubular Thermoelectric Generator T>

Next, a detailed configuration for the tubular thermoelectric generatorT will be described with reference to FIGS. 6A and 6B. FIG. 6A is aperspective view illustrating one of the tubular thermoelectricgenerators T (e.g., the tubular thermoelectric generator T1 in thisexample) that the thermoelectric generator unit 100 has. The tubularthermoelectric generator T1 includes a tube body Tb1 and first andsecond electrodes E1 and E2 which are arranged at both ends of the tubebody Tb1. The tube body Tb1 has a configuration in which multiple metallayers 20 and multiple thermoelectric material layers 22 are alternatelystacked one upon the other. In the present specification, the directionin which a line that connects the first and second electrodes E1 and E2together runs will sometimes be referred to as a “stacking direction”hereinbelow. The stacking direction agrees with the axial direction ofthe tubular thermoelectric generator.

FIG. 6B schematically illustrates a cross section of the tubularthermoelectric generator T1 as viewed on a plane including the axis(center axis) of the tubular thermoelectric generator T1. As shown inFIG. 6B, the tubular thermoelectric generator T1 has an outer peripheralsurface 24 and an inner peripheral surface 26. A region which is definedby the inner peripheral surface 26 forms a flow path F1. In theillustrated example, cross sections of the outer peripheral surface 24and the inner peripheral surface 26 taken perpendicular to the axialdirection each present the shape of a circle. However, these shapes arenot limited to circles, but may be ellipses or polygons, as describedabove. The cross-sectional area of the flow path on such a cross sectionthat intersects with the axial direction at right angles is notparticularly limited. The cross-sectional area of the flow path or thenumber of tubular thermoelectric generators to provide may be determinedappropriately by the flow rate of the medium to be supplied into theinternal flow path of the tubular thermoelectric generator T.

Although the first and second electrodes E1 and E2 each have a circularcylindrical shape in the example illustrated in FIGS. 6A and 6B, this isonly an example and the first and second electrodes E1 and E2 do notneed to have such a shape. At or near the respective end of the tubebody Tb1, the first electrode E1 and the second electrode E2 may eachhave any arbitrary shape which is electrically connectable to at leastone of the metal layers 20 or the thermoelectric material layers 22 andwhich does not obstruct the flow path F1. In the example shown in FIGS.6A and 6B, the first electrode E1 and the second electrode E2 have outerperipheral surfaces conforming to the outer peripheral surface 24 of thetube body Tb1; however, it is not necessary for the outer peripheralsurfaces of the first electrode E1 and the second electrode E2 toconform to the outer peripheral surface 24 of the tube body Tb1. Forexample, the diameter of the outer peripheral surface (i.e., the outerdiameter) of the first and second electrodes E1 and E2 may be larger orsmaller than that of the tube body Tb1. Also, when viewed on a planethat intersects with the axial direction at right angles, thecross-sectional shape of the first and second electrodes E1 and E2 maybe different from that of the outer peripheral surface 24 of the tubebody Tb1.

The first and second electrodes E1 and E2 may be made of a material withelectrical conductivity and are typically made of a metal. The first andsecond electrodes E1 and E2 may be comprised of a single or multiplemetal layers 20 which are located at or near the ends of the tube bodyTb1. In that case, portions of the tube body Tb1 function as the firstand second electrodes E1 and E2. Alternatively, the first and secondelectrodes E1 and E2 may also be formed out of a metal layer or annularmetallic member which is arranged so as to partially cover the outerperipheral surface of the tube body Tb1. Still alternatively, the firstand second electrodes E1 and E2 may also be a pair of circularcylindrical metallic members which are fitted into the flow path F1through the ends of the tube body Tb1 so as to be in contact with theinner peripheral surface of the tube body Tb1.

As shown in FIG. 6B, the metal layers 20 and thermoelectric materiallayers 22 are alternately stacked one upon the other so as to beinclined. A tubular thermoelectric generator with such a configurationoperates on basically the same principle as what has already beendescribed with reference to FIGS. 1A, 1B and 2. That is why if atemperature difference is created between the outer peripheral surface24 and inner peripheral surface 26 of the tubular thermoelectricgenerator T1, a potential difference is generated between the first andsecond electrodes E1 and E2. The general direction of the temperaturegradient is the radial direction of the tubular thermoelectric generatorT1 (i.e., the direction that intersects with the stacking direction atright angles).

The inclination angle θ of the planes of stacking in the tube body Tb1may be set within the range of not less than 5 degrees and not more than60 degrees, for example. The inclination angle θ may be not less than 20degrees and not more than 45 degrees. An appropriate range of theinclination angle θ varies according to the combination of the materialto make the metal layers 20 and the thermoelectric material to make thethermoelectric material layers 22.

The ratio of the thickness of each metal layer 20 to that of eachthermoelectric material layer 22 in the tube body Tb1 (which will behereinafter simply referred to as a “stacking ratio”) may be set withinthe range of 20:1 to 1:9, for example. In this case, the thickness ofthe metal layer 20 refers herein to its thickness as measuredperpendicularly to the plane of stacking (i.e., the thickness indicatedby the arrow Th in FIG. 6B). In the same way, the thickness of thethermoelectric material layer 22 refers herein to its thickness asmeasured perpendicularly to the plane of stacking. It should be notedthat the total number of the metal layers 20 and thermoelectric materiallayers 22 that are stacked one upon the other may be set appropriately.

The metal layers 20 may be made of any arbitrary metallic material. Forexample, the metal layers 20 may be made of nickel or cobalt. Nickel andcobalt are examples of metallic materials which exhibit excellentthermoelectric generation properties. Optionally, the metal layers 20may include silver or gold. Furthermore, the metal layers 20 may includeany of these metallic materials either by itself or as their alloy. Ifthe metal layers 20 are made of an alloy, the alloy may include copper,chromium or aluminum. Examples of such alloys include constantan,CHROMEL™, and ALUMEL™.

The thermoelectric material layers 22 may be made of any arbitrarythermoelectric material depending on their operating temperature.Examples of thermoelectric materials which may be used to make thethermoelectric material layers include: thermoelectric materials of asingle element, such as bismuth or antimony; alloy-type thermoelectricmaterials, such as BiTe-type, PbTe-type and SiGe-type; and oxide-typethermoelectric materials, such as Ca_(x)CoO₂, Na_(x)CoO₂ and SrTiO₃. Inthe present specification, the “thermoelectric material” refers hereinto a material, of which the Seebeck coefficient has an absolute value of30 μV/K or more and the electrical resistivity is 10 mΩ cm or less. Sucha thermoelectric material may be a crystalline one or an amorphous one.If the hot medium has a temperature of approximately 200 degrees Celsiusor less, the thermoelectric material layers 22 may be made of a densebody of bismuth-antimony-tellurium, for example.Bismuth-antimony-tellurium may be, but does not have to be, representedby a chemical composition Bi_(0.5)Sb_(1.5)Te₃. Optionally,bismuth-antimony-tellurium may include a dopant such as selenium. Themole fractions of bismuth and antimony may be adjusted appropriately.

Other examples of the thermoelectric materials to make thethermoelectric material layers 22 include bismuth telluride and leadtelluride. When the thermoelectric material layers 22 are made ofbismuth telluride, it may be of the chemical composition Bi₂Te_(x),where 2<X<4. A representative chemical composition of bismuth tellurideis Bi₂Te₃, which may include antimony or selenium. The chemicalcomposition of bismuth telluride including antimony may be representedby (Bi_(1-Y)Sb_(Y))₂Te_(X), where 0<Y<1, and more preferably 0.6<Y<0.9.

The first and second electrodes E1 and E2 may be made of any material aslong as the material has good electrical conductivity. For example, thefirst and second electrodes E1 and E2 may be made of a metal selectedfrom the group consisting of nickel, copper, silver, molybdenum,tungsten, aluminum, titanium, chromium, gold, platinum and indium.Alternatively, the first and second electrodes E1 and E2 may also bemade of a nitrides or oxides, such as titanium nitride (TiN), indium tinoxide (ITO), and tin dioxide (SnO₂). Still alternatively, the first orsecond electrode E1, E2 may also be made of solder, silver solder orelectrically conductive paste, for example. It should be noted that ifboth ends of the tube body Tb1 are metal layers 20, then the first andsecond electrodes E1 and E2 may be replaced with those metal layers 20as described above.

In the foregoing description, an element with a configuration in whichmetal layers and thermoelectric material layers are alternately stackedone upon the other has been described as a typical example of a tubularthermoelectric generator. However, this is just an example, and thetubular thermoelectric generator which may be used according to thepresent disclosure does not need to have such a configuration. Ratherelectrical power can also be generated thermoelectrically as describedabove as long as a first layer made of a first material with arelatively low Seebeck coefficient and relatively high thermalconductivity and a second layer made of a second material with arelatively high Seebeck coefficient and relatively low thermalconductivity are stacked alternately one upon the other. That is to say,the metal layer 20 and thermoelectric material layer 22 are onlyexamples of such first and second layers, respectively.

<Implementation of Thermoelectric Generator Unit>

Next, look at FIGS. 7A and 7B. FIG. 7A is a front view illustrating animplementation of a thermoelectric generator unit that thethermoelectric generator system according to the present disclosure has,and FIG. 7B illustrates one of the side surfaces of the thermoelectricgenerator unit 100 (a right side view in this case). As shown in FIG.7A, the thermoelectric generator unit 100 according to thisimplementation includes a number of tubular thermoelectric generators Tand a container 30 which houses those tubular thermoelectric generatorsT inside. At a glance, such a structure looks like the “shell and tubestructure” of a heat exchanger. In a heat exchanger, however, a numberof tubes just function as pipelines to make fluid flow through and donot have to be electrically connected together. In a thermoelectricgenerator system according to the present disclosure, on the other hand,those tubular thermoelectric generators need to be electricallyconnected together in practice with good stability, unlike the heatexchanger.

As already described with reference to FIG. 4, a hot medium and a coldmedium are supplied to the thermoelectric generator unit 100. The hotmedium may be supplied into the respective internal flow paths of thetubular thermoelectric generators T1 to T10 through multiple openings A,for example. Meanwhile, the cold medium is supplied into the container30 through a fluid inlet port 38 a to be described later. As a result, atemperature difference is created between the outer and inner peripheralsurfaces of each tubular thermoelectric generator T. In this case, inthe thermoelectric generator unit 100, not only heat is exchangedbetween the hot and cold media but also electromotive force occurs inthe axial direction in each of the tubular thermoelectric generators T1to T10.

In this embodiment, the container 30 includes a cylindrical shell 32which surrounds the tubular thermoelectric generators T and a pair ofplates 34 and 36 which are arranged to close the open ends of the shell32. More specifically, the plates 34 and 36 are respectively fixed ontothe left and right ends of the shell 32. Each of these plates 34 and 36has multiple openings A into which respective tubular thermoelectricgenerators T are inserted. Both ends of an associated tubularthermoelectric generator T are inserted into each corresponding pair ofopenings A of the plates 34 and 36.

Just like the tube sheets of a shell and tube heat exchanger, theseplates 34 and 36 have the function of supporting a plurality of tubes(i.e., the tubular thermoelectric generators T) so that these tubes arespatially separated from each other. However, as will be described indetail later, the plates 34 and 36 of this embodiment have an electricalconnection capability that the tube sheets of a heat exchanger do nothave.

In the example illustrated in FIG. 7A, the plate 34 includes a firstplate portion 34 a fixed to the shell 32 and a second plate portion 34 bwhich is attached to the first plate portion 34 a so as to be readilyremovable from the first plate portion 34 a. Likewise, the plate 36 alsoincludes a first plate portion 36 a fixed to the shell 32 and a secondplate portion 36 b which is attached to the first plate portion 36 a soas to be readily removable from the first plate portion 36 a. Theopenings A in the plates 34 and 36 penetrate through, respectively, thefirst plate portions 34 a and 36 a and the second plate portions 34 band 36 b, thus leaving the flow paths of the thermoelectric generationtubes T open to the exterior of the container 30.

Examples of materials to make the container 30 include metals such asstainless steel, HASTELLOY™ or INCONEL™. Examples of other materials tomake the container 30 include polyvinyl chloride and acrylic resin. Theshell 32 and the plates 34, 36 may be made of the same material or maybe made of two different materials. If the shell 32 and the first plateportions 34 a and 36 a are made of metal(s), then the first plateportions 34 a and 36 a may be welded onto the shell 32. Or if flangesare provided at both ends of the shell 32, the first plate portions 34 aand 36 a may be fixed onto those flange portions.

Since some fluid (that is either the cold medium or hot medium) isintroduced into the container 30 while the thermoelectric generator unit100 is operating, the inside of the container 30 should be kept eitherairtight or watertight. As will be described later, each opening A ofthe plates 34, 36 is sealed to keep the inside of the container 30either airtight or watertight once the ends of the tubularthermoelectric generator T have been inserted through the opening A. Astructure in which no gap is left between the shell 32 and the plates34, 36 and which is kept either airtight or watertight throughout theoperation is realized.

As shown in FIG. 7B, ten openings A have been cut through the plate 36.Likewise, ten openings A have also been cut through the other plate 34.In the example illustrated in FIGS. 7A and 7B, each opening A of theplate 34 and its associated opening A of the plate 36 are arrangedmirror-symmetrically to each other, and ten lines which connect togetherthe respective center points of ten pairs of associated openings A areparallel to each other. According to such a configuration, therespective tubular thermoelectric generators T may be supported parallelto each other through the pairs of associated openings A. Nevertheless,those tubular thermoelectric generators T do not have to be arrangedparallel to each other inside the container 30 but may also be arrangedeither non-parallel or skew to each other.

As shown in FIG. 7B, the plate 36 has channels C, each of which has beenformed to connect together at least two of the openings A cut throughthe plate 36 and will sometimes be referred to as a “interconnections”hereinbelow. In the example illustrated in FIG. 7B, the channel C61connects together openings A61 and A62. Each of the other channels C62to C65 also connects together two associated ones of the openings A inthe plate 36. As will be described later, an electrically conductivemember is housed in each of these channels C61 to C65.

FIG. 8 schematically illustrates a portion of a cross section of thethermoelectric generator unit 100 as viewed on the plane M-M shown inFIG. 7B. It should be noted that in FIG. 8, a cross section of the lowerhalf of the container 30 is not shown but its front portion is showninstead. As shown in FIG. 8, the container 30 has a fluid inlet port 38a and a fluid outlet port 38 b through which a fluid flows inside thecontainer 30. In this thermoelectric generator unit 100, the fluid inletand outlet ports 38 a and 38 b are arranged in the upper part of thecontainer 30. However, the fluid inlet port 38 a does not have to bearranged in the upper part of the container 30 but may also be arrangedin the lower part of the container 30 as well. The same can be saidabout the fluid outlet port 38 b. The fluid inlet and outlet ports 38 aand 38 b do not always have to be used as inlet and outlet for a fluidbut may be inverted at regular or irregular intervals. That is to say,the fluid flow direction does not have to be fixed. Also, although onlyone fluid inlet port 38 a and only one fluid outlet port 38 b are shownin FIG. 8, this is only an example, and more than one fluid inlet port38 a and/or more than one fluid outlet port 38 b may be provided aswell.

FIG. 9 schematically shows exemplary flow directions of the hot and coldmedia introduced into the thermoelectric generator unit 100. In theexample shown in FIG. 9, a hot medium HM is supplied into the internalflow path of each of the tubular thermoelectric generators T1 to T10,while a cold medium LM is supplied into the container 30. In thisexample, the hot medium HM is introduced into the internal flow path ofeach tubular thermoelectric generator through the openings A cut throughthe plate 34. The hot medium HM introduced into the internal flow pathof each tubular thermoelectric generator contacts with the innerperipheral surface of the tubular thermoelectric generator. On the otherhand, the cold medium LM is introduced into the container 30 through thefluid inlet port 38 a. The cold medium LM introduced into the container30 contacts with the outer peripheral surface of each tubularthermoelectric generator.

In the example shown in FIG. 9, while flowing through the internal flowpath of each tubular thermoelectric generator, the hot medium HMexchanges heat with the cold medium LM. The hot medium HM, of which thetemperature has decreased through heat exchange with the cold medium LM,is discharged out of the thermoelectric generator unit 100 through theopenings A of the plate 36. On the other hand, while flowing inside thecontainer 30, the cold medium LM exchanges heat with the hot medium HM.The cold medium LM, of which the temperature has increased through heatexchange with the hot medium HM, is discharged out of the thermoelectricgenerator unit 100 through the fluid outlet port 38 b. The flowdirections of the hot and cold media HM and LM shown in FIG. 9 are onlyan example. One or both of the hot and cold media HM and LM may flowfrom the right to the left on the paper.

In one implementation, the hot medium HM (e.g., hot water) may beintroduced into the flow path of each tubular thermoelectric generatorT, and the cold medium LM (e.g., cooling water) may be introducedthrough the fluid inlet port 38 a to fill the inside of the container 30with the cold medium LM. Conversely, the cold medium LM (e.g., coolingwater) may be introduced into the flow path of each tubularthermoelectric generator T, and the hot medium HM (e.g., hot water) maybe introduced through the fluid inlet port 38 a to fill the inside ofthe container 30 with the hot medium HM. In this manner, a temperaturedifference which is large enough to generate electric power can becreated between the outer and inner peripheral surfaces 24 and 26 ofeach tubular thermoelectric generator T.

<Implementations of Sealing from Fluids and Electrical ConnectionBetween Tubular Thermoelectric Generators>

Portion (a) of FIG. 10 schematically illustrates a partialcross-sectional view of the plate 36. Specifically, portion (a) of FIG.10 schematically illustrates a cross section of the plate 36 as viewedon a plane including the respective center axes of both of two tubularthermoelectric generators T1 and T2. More specifically, portion (a) ofFIG. 10 illustrates the structure of openings A61 and A62 of multipleopenings A that the plate 36 has and a region surrounding them. Portion(b) of FIG. 10 schematically illustrates the appearance of anelectrically conductive member J1 as viewed in the direction indicatedby the arrow V1 in portion (a) of FIG. 10. This electrically conductivemember J1 has two through holes Jh1 and Jh2. In detail, thiselectrically conductive member J1 includes a first ring portion Jr1 withthe through hole Jh1, a second ring portion Jr2 with the through holeJh2, and a connecting portion Jc to connect these two ring portions Jr1and Jr2 together.

As shown in portion (a) of FIG. 10, one end of the tubularthermoelectric generator T1 (on the second electrode side) is insertedinto the opening A61 of the plate 36 and one end of the tubularthermoelectric generator T2 (on the first electrode side) is insertedinto the opening A62. In this state, those ends of the tubularthermoelectric generators T1 and T2 are respectively inserted into thethrough holes Jh1 and Jh2 of the electrically conductive member J1. Thatend of the tubular thermoelectric generator T1 (on the second electrodeside) and that of the tubular thermoelectric generator T2 (on the firstelectrode side) are electrically connected together via thiselectrically conductive member J1. In the present specification, anelectrically conductive member to connect two tubular thermoelectricgenerators electrically together will be hereinafter referred to as a“connection plate”.

It should be noted that the first and second ring portions Jr1 and Jr2do not need to have an annular shape. As long as electrical connectionis established between the tubular thermoelectric generators, thethrough hole Jh1 or Jh2 may also have a circular, elliptical orpolygonal shape as well. For example, the shape of the through hole Jh1or Jh2 may be different from the cross-sectional shape of the first orsecond electrode E1 or E2 as viewed on a plane that intersects with theaxial direction at right angles. In the present specification, the“ring” shape includes not only an annular shape but other shapes aswell.

In the example illustrated in portion (a) of FIG. 10, the first plateportion 36 a has a recess R36 which has been cut for the openings A61and A62. This recess R36 includes a groove portion R36 c to connect theopenings A61 and A62 together. The connecting portion Jc of theelectrically conductive member J1 is located in this groove portion R36c. On the other hand, recesses R61 and R62 have been cut in the secondplate portion 36 b for the openings A61 and A62, respectively. In thisexample, various members to establish sealing and electrical connectionare arranged inside the space formed by these recesses R36, R61 and R62.That space forms a channel C61 to house the electrically conductivemember J1 and the openings A61 and A62 are connected together via thechannel C61.

In the example illustrated in portion (a) of FIG. 10, not only theelectrically conductive member J1 but also a first O-ring 52 a, washers54, an electrically conductive ring member 56 and a second O-ring 52 bare housed in the channel C61. The respective ends of the tubularthermoelectric generators T1 and T2 go through the holes of thesemembers. The first O-ring 52 a arranged closest to the shell 32 of thecontainer 30 is in contact with the seating surface Bsa that has beenformed in the first plate portion 36 a and establishes sealing so as toprevent a fluid that has been supplied into the shell 32 from enteringthe channel C61. On the other hand, the second O-ring 52 b arranged mostdistant from the shell 32 of the container 30 is in contact with aseating surface Bsb that has been formed in the second plate portion 36b and establishes sealing so as to prevent a fluid located outside ofthe second plate portion 36 b from entering the channel C61.

The O-rings 52 a and 52 b are annular seal members with an O (i.e.,circular) cross section. The O-rings 52 a and 52 b may be made ofrubber, metal or plastic, for example, and have the function ofpreventing a fluid from leaking out, or flowing into, through a gapbetween the members. In portion (a) of FIG. 10, there is a space whichcommunicates with the flow paths of the respective tubularthermoelectric generators T on the right-hand side of the second plateportion 36 b and there is a fluid (the hot or cold medium in thisexample) in that space. According to this embodiment, by using themembers shown in FIG. 10, electrical connection between the tubularthermoelectric generators T and sealing from the fluids (the hot andcold media) are established. The structure and function of theelectrically conductive ring member 56 will be described in detaillater.

The same members as the ones described for the plate 36 are provided forthe plate 34, too. Although the respective openings A of the plates 34and 36 are arranged mirror symmetrically, the groove portions connectingany two openings A together on the plate 34 are not arranged mirrorsymmetrically with the groove portions connecting any two openings Atogether on the plate 36. If the arrangement patterns of theelectrically conductive members to electrically connect the tubularthermoelectric generators T together on the plates 34 and 36, weremirror symmetric to each other, then those tubular thermoelectricgenerators T could not be connected together in series.

If a plate (such as the plate 36) fixed onto the shell 32 includes firstand second plate portions (36 a and 36 b) as in this embodiment, each ofthe multiple openings A cut through the first plate portion (36 a) has afirst seating surface (Bsa) associated therewith to receive the firstO-ring 52 a, and each of the multiple openings A cut through the secondplate portion (36 b) has a second seating surface (Bsb) to receive thesecond O-ring 52 b. However, the plates 34 and 36 do not need to havethe configuration shown in FIG. 10 and the plate 36 does not have to bedivided into the first and second plate portions 36 a and 36 b, either.If the electrically conductive member J1 is pressed by another memberinstead of the second plate portion 36 b, the respective first O-rings52 a press against the first seating surface (Bsa) to establish sealing,too.

In the example shown in portion (a) of FIG. 10, the electricallyconductive ring member 56 is interposed between the tubularthermoelectric generator T1 and the electrically conductive member J1.Likewise, another electrically conductive ring member 56 is interposedbetween the tubular thermoelectric generator T2 and the electricallyconductive member J1, too.

The electrically conductive member J1 is typically made of a metal.Examples of materials to make the electrically conductive member J1include copper (oxygen-free copper), brass and aluminum. The materialmay be plated with nickel or tin for anticorrosion purposes. As long aselectrical connection is established between the electrically conductivemember J (e.g., J1 in this example) and the tubular thermoelectricgenerators T (e.g., T1 and T2 in this example) inserted into the twothrough holes of the electrically conductive member J (e.g., Jh1 and Jh2in this example), the electrically conductive member J may be partiallycoated with an insulator. That is to say, the electrically conductivemember J may include a body made of a metallic material and aninsulating coating which covers the surface of the body at leastpartially. The insulating coating may be made of a resin such asTEFLON™, for example. If the body of the electrically conductive memberJ is made of aluminum, the surface may be partially coated with an oxideskin as an insulating coating.

FIG. 11A is an exploded perspective view schematically illustrating thechannel C61 to house the electrically conductive member J1 and itsvicinity. As shown in FIG. 11A, the first O-rings 52 a, electricallyconductive ring members 56, electrically conductive member J1 and secondO-rings 52 b are inserted into the openings A61 and A62 from outside ofthe container 30. In this example, washers 54 are arranged between thefirst O-rings 52 a and the electrically conductive ring members 56.Washers 54 may also be arranged between the electrically conductivemember J1 and the second O-rings 52 b. The washers 54 are insertedbetween the flat portions 56 f of the electrically conductive ringmembers 56 to be described later and the O-rings 52 a (or 52 b).

FIG. 11B schematically illustrates a portion of the sealing surface ofthe second plate portion 36 b (i.e., the surface that faces the firstplate portion 36 a) associated with the openings A61 and A62. Asdescribed above, the openings A61 and A62 of the second plate portion 36b each have a seating surface Bsb to receive the second O-ring 52 b.That is why if the respective sealing surfaces of the first and secondplate portions 36 a and 36 b are arranged to face each other andfastened together by flange connection, for example, the first O-rings52 a in the first plate portion 36 a can be pressed against the seatingsurfaces Bsa. More specifically, the second seating surfaces Bsb pressthe first O-rings 52 a against the seating surfaces Bsa through thesecond O-rings 52 b, electrically conductive member J1 and electricallyconductive ring members 56. In this manner, the electrically conductivemember J1 can be sealed from the hot and cold media.

If the first and second plate portions 36 a and 36 b are made of anelectrically conductive material such as a metal, then the sealingsurfaces of the first and second plate portions 36 a and 36 b may becoated with an insulator material. Parts of the first and second plateportions 36 a and 36 b to contact with the electrically conductivemember J during operation may be coated with an insulator so as to beelectrically insulated from the electrically conductive member J. In oneimplementation, the sealing surfaces of the first and second plateportions 36 a and 36 b may be sprayed and coated with a fluoroethyleneresin.

<Detailed Configuration for Electrically Conductive Ring Members>

A detailed configuration for the electrically conductive ring members 56will be described with reference to FIGS. 12A and 12B.

FIG. 12A is a perspective view illustrating an exemplary shape of anelectrically conductive ring member 56. The electrically conductive ringmember 56 shown in FIG. 12A includes a ringlike flat portion 56 f and aplurality of elastic portions 56 r. The flat portion 56 f has a throughhole 56 a. Those elastic portions 56 r project from around the peripheryof the through hole 56 a of the flat portion 56 f and are biased towardthe center of the through hole 56 a with elastic force. Such anelectrically conductive ring member 56 can be made easily by patterninga single metallic plate (with a thickness of 0.1 mm to a few mm, forexample). Likewise, the electrically conductive members J can also bemade easily by patterning a single metallic plate (with a thickness of0.1 mm to a few mm, for example).

An end (on the first or second electrode side) of an associated tubularthermoelectric generator T is inserted into the through hole 56 a ofeach electrically conductive ring member 56. That is why the shape andsize of the through hole 56 a of the ringlike flat portion 56 f aredesigned so as to match the shape and size of that end (on the first orsecond electrode side) of the tubular thermoelectric generator T.

Next, the shape of the electrically conductive ring member 56 will bedescribed in further detail with reference to FIGS. 13A, 13B and 13C.FIG. 13A is a cross-sectional view schematically illustrating portionsof the electrically conductive ring member 56 and tubular thermoelectricgenerator T1. FIG. 13B is a cross-sectional view schematicallyillustrating a state where an end of the tubular thermoelectricgenerator T1 has been inserted into the electrically conductive ringmember 56. And FIG. 13C is a cross-sectional view schematicallyillustrating a state where an end of the tubular thermoelectricgenerator T1 has been inserted into the respective through holes of theelectrically conductive ring member 56 and electrically conductivemember J1. The cross sections illustrated in FIGS. 13A, 13B and 13C areviewed on a plane including the axis (i.e., the center axis) of thetubular thermoelectric generator T1.

Suppose the outer peripheral surface of the tubular thermoelectricgenerator T1 at that end (on the first or second electrode side) is acircular cylinder with a diameter D as shown in FIG. 13A. In that case,the through hole 56 a of the electrically conductive ring member 56 isformed in a circular shape with a diameter D+δ1 (where δ1>1) so as topass the end of the tubular thermoelectric generator T1. On the otherhand, the respective elastic portions 56 r have been formed so thatbiasing force is applied toward the center of the through hole 56 a. Therespective elastic portions 56 r may be formed so as to be tilted towardthe center of the through hole 56 a as shown in FIG. 13A. That is tosay, the elastic portions 56 r have been shaped so as to becircumscribed with the outer peripheral surface of a circular cylinder,of which a cross section has a diameter that is smaller than D (and thatis represented by D−δ2 (where δ2>0)) unless any external force isapplied.

D+δ1>D>D−δ2 is satisfied. That is why when the end of the tubularthermoelectric generator T1 is inserted into the through hole 56 a, therespective elastic portions 56 r are brought into physical contact withthe outer peripheral surface at the end of the tubular thermoelectricgenerator T1 as shown in FIG. 13B. In this case, since elastic force isapplied to the respective elastic portions 56 r toward the center of thethrough hole 56 a, the respective elastic portions 56 r press the outerperipheral surface at the end of the tubular thermoelectric generator T1with the elastic force. In this manner, the outer peripheral surface ofthe tubular thermoelectric generator T1 inserted into the through hole56 a establishes stabilized physical and electrical contact with thoseelastic portions 56 r.

Next, look at FIG. 13C. Inside the opening A cut through the plate 34,36, the electrically conductive member J1 contacts with the flat portion56 f of the electrically conductive ring member 56. More specifically,when the end of the tubular thermoelectric generator T1 is inserted intothe electrically conductive ring member 56 and electrically conductivemember J1, the surface of the flat portion 56 f of the electricallyconductive ring member 56 contacts with the surface of the ring portionJr1 of the electrically conductive member J1 as shown in FIG. 13C. Ascan be seen, in this embodiment, the electrically conductive ring member56 and the electrically conductive member J1 may be electricallyconnected together by bringing their planes into contact with eachother. Since the electrically conductive ring member 56 and theelectrically conductive member J1 contact with each other on theirplanes, a contact area which is large enough to make the electriccurrent generated in the tubular thermoelectric generator T1 flow can besecured. The width W of the flat portion 56 f is set appropriately tosecure a contact area which is large enough to make the electric currentgenerated in the tubular thermoelectric generator T1 flow. As long as acontact area can be secured between the electrically conductive ringmember 56 and the electrically conductive member J1, either the surfaceof the flat portion 56 f or the surface of the ring portion Jr1 of theelectrically conductive member J1 may have some unevenness. For example,an even larger area of contact can be secured by making the surface ofthe ring portion Jr1 of the electrically conductive member J1 have anembossed pattern matching the one on the surface of the flat portion 56f.

Next, look at FIGS. 14A and 14B. FIG. 14A is a cross-sectional viewschematically illustrating the electrically conductive ring member 56and a portion of the electrically conductive member J1. FIG. 14B is across-sectional view schematically illustrating a state where theelastic portions 56 r of the electrically conductive ring member 56 havebeen inserted into the through hole Jh1 of the electrically conductivemember J1. The cross sections shown in FIGS. 14A and 14B are obtained byviewing the electrically conductive ring member 56 and the electricallyconductive member J1 on a plane including the axis (center axis) of thetubular thermoelectric generator T1.

If the diameter of the through hole (e.g., Jh1 in this case) of theelectrically conductive member J is supposed to be 2Rr, the through holeof the electrically conductive member J is formed to satisfy D<2Rr(i.e., so as to pass the end of the tubular thermoelectric generator T1through itself). Also, if the diameter of the flat portion 56 f of theelectrically conductive ring member 56 is supposed to be 2Rf, thethrough hole of the electrically conductive member J is formed tosatisfy 2Rr<2Rf so that the respective surfaces of the flat portion 56 fand ring portion Jr1 contact with each other just as intended.

Optionally, the end of the tubular thermoelectric generator T may have achamfered portion Cm as shown in FIG. 15. The reason is that when theend of the tubular thermoelectric generator T (e.g., tubularthermoelectric generator T1) is inserted into the through hole 56 a ofthe electrically conductive ring member 56, the elastic portions 56 r ofthe electrically conductive ring member 56 and the end of the tubularthermoelectric generator T contact with each other, thus possiblygetting the end of the tubular thermoelectric generator T damaged.However, by providing such a chamfered portion Cm at the end of thetubular thermoelectric generator T, such damage that could be done onthe end of the tubular thermoelectric generator T due to the contactbetween the elastic portions 56 r and the end of the tubularthermoelectric generator T can be avoided. And by avoiding theoccurrence of the damage on the end of the tubular thermoelectricgenerator T, the electrically conductive member J can be sealed moresecurely from the hot and cold media. In addition, electrical contactfailure between the outer peripheral surface of the tubularthermoelectric generator T and the elastic portions 56 r can also bereduced. The chamfered portion Cm may have the curved surface as shownin FIG. 15 or may also have a planar surface.

In this manner, the electrically conductive member J1 is electricallyconnected to the outer peripheral surface at the end of the tubularthermoelectric generator T via the electrically conductive ring member56. According to this embodiment, by fastening the first and secondplate portions 36 a and 36 b together, the flat portion 56 f of theelectrically conductive ring member 56 and the electrically conductivemember J can make electrical contact with each other with good stabilityand sealing described above can be established.

Furthermore, by arranging the electrically conductive ring member 56with respect to the end of the tubular thermoelectric generator T, theelectrically conductive member J1 can be sealed more tightly. Asdescribed above, the first O-ring 52 a is pressed against the seatingsurface Bsa via the electrically conductive member J1 and theelectrically conductive ring member 56. In this case, the electricallyconductive ring member 56 has the flat portion 56 f. That is to say, thepressure is applied to the first O-ring 52 a through the flat portion 56f of the electrically conductive ring member 56. That is to say, sincethe electrically conductive ring member 56 has the flat portion 56 f,the pressure can be applied evenly to the first O-ring 52 a. As aresult, the first O-ring 52 a can be pressed against the seating surfaceBsa firmly enough to get sealing done just as intended from the fluid inthe container. In the same way, proper pressure can also be applied tothe second O-ring 52 b, and therefore, sealing can be done from thefluid outside of the container, too.

Next, it will be described how the electrically conductive ring member56 may be fitted into the tubular thermoelectric generator T.

First of all, as shown in FIG. 11A, the respective ends of the tubularthermoelectric generators T1 and T2 are inserted into the openings A61and A62 of the first plate portion 36 a. After that, the first O-rings52 a (and the washers 54 if necessary) are fitted into the tubularthermoelectric generators through their tip ends and pushed deeper intothe openings A61 and A62. Next, the electrically conductive ring members56 are fitted into the tubular thermoelectric generators through theirtip ends and pushed deeper into the openings A61 and A62. Subsequently,the electrically conductive member J1 (and the washers 54 and secondO-rings 52 b if necessary) is/are fitted into the tubular thermoelectricgenerators through their tip ends and pushed deeper into the openingsA61 and A62. Finally, the sealing surface of the second plate portion 36b is arranged to face the first plate portion 36 a and the first andsecond plate portions 36 a and 36 b are fastened together by flangeconnection, for example, so that the respective tip ends of the tubularthermoelectric generators are inserted into the openings of the secondplate portion 36 b. In this case, the first and second plate portions 36a and 36 b may be fastened together with bolts and nuts through theholes 36 bh cut through the second plate portion 36 b (shown in FIG. 7B)and the holes cut through the first plate portion 36 a.

The electrically conductive ring member 56 is not connected permanentlyto, and is readily removable from, the tubular thermoelectric generatorT. For example, when the tubular thermoelectric generator T is replacedwith a new tubular thermoelectric generator T, to remove theelectrically conductive ring member 56 from the tubular thermoelectricgenerator T, the operation of fitting the electrically conductive ringmembers 56 into the tubular thermoelectric generators T may be performedin reverse order. The electrically conductive ring member 56 may be useda number of times (i.e., is recyclable) or replaced with a new one.

The electrically conductive ring member 56 does not always need to havethe exemplary shape shown in FIG. 12A. The ratio of the width of theflat portion 56 f (as measured radially) to the radius of the throughhole 56 a may also be defined arbitrarily. The respective elasticportions 56 r may have any of various shapes and the number of theelastic portions 56 r to provide may be set arbitrarily, too.

FIG. 12B is a perspective view illustrating another exemplary shape ofthe electrically conductive ring member 56. The electrically conductivering member 56 shown in FIG. 12B also has a ringlike flat portion 56 fand a plurality of elastic portions 56 r. The flat portion 56 f has athrough hole 56 a. Each of the elastic portions 56 r projects fromaround the through hole 56 a of the flat portion 56 f and is biasedtoward the center of the through hole 56 a with elastic force. In thisexample, the number of the elastic portions 56 r to provide is four. Thenumber of the elastic portions 56 r may be two but is suitably three ormore. For example, six or more elastic portions 56 r may be provided.

It should be noted that according to such an arrangement in which theflat-plate electrically conductive member J is brought into contact withthe flat portion 56 f of the electrically conductive ring member 56,some gap (or clearance) may be left between the through hole inside thering portion of the electrically conductive member J and the tubularthermoelectric generator to be inserted into the hole. Thus, even if thetubular thermoelectric generator is made of a brittle material, thetubular thermoelectric generator can also be connected with goodstability without allowing the ring portion Jr1 of the electricallyconductive member J to do damage on the tubular thermoelectricgenerator.

<Electrical Connection Via Connection Plate>

As described above, the electrically conductive member (connectionplate) is housed inside the channel C which has been cut to interconnectat least two of the openings A that have been cut through the plate 36.Note that the respective ends of the two tubular thermoelectricgenerators may be electrically connected together without theelectrically conductive ring members 56. In other words, theelectrically conductive ring members 56 may be omitted from the channelC. In that case, the respective ends of the two tubular thermoelectricgenerators may be electrically connected together via an electric cord,a conductor bar, or electrically conductive paste, for example. If theends of the two tubular thermoelectric generators are electricallyconnected together via an electric cord, those ends of the tubularthermoelectric generators and the cord may be electrically connectedtogether by soldering, crimping or crocodile-clipping, for example.

However, by electrically connecting the respective ends of the twotubular thermoelectric generators via the electrically conductive memberthat is housed in the channel C as shown in FIGS. 10, 11A and 11B, therespective ends of the tubular thermoelectric generators T and theelectrically conductive member J1 can be electrically connected togethermore stably. If the electrically conductive member J has a flat plateshape (e.g., if the connecting portion Jc has a broad width), theelectrical resistance between the two tubular thermoelectric generatorscan be reduced compared to a situation where an electric cord is used.In addition, since no terminals are fixed onto the ends of the tubularthermoelectric generators T, the tubular thermoelectric generators T canbe replaced easily. Alternatively, with the electrically conductive ringmembers 56, the respective ends of the two tubular thermoelectricgenerators can be not only fixed to each other but also electricallyconnected together.

In the thermoelectric generator unit 100, the plate or 36 has thechannel C which has been cut to connect together at least two of theopenings A, and therefore, electrical connecting function which hasnever been provided by any tube sheet for a heat exchanger is realized.In addition, since the thermoelectric generator unit 100 can beconfigured so that the first and second O-rings 52 a and 52 b press theseating surfaces Bsa and Bsb, respectively, sealing can be establishedso that either airtight or watertight condition is maintained with theends of the tubular thermoelectric generators T inserted. As can beseen, by providing the channel C for the plate 34 or 36, even in animplementation in which the electrically conductive ring members 56 areomitted, the ends of the two tubular thermoelectric generators can alsobe electrically connected together and sealing from the fluids (e.g.,the hot and cold media) can also be established.

<Relation Between Direction of Flow of Heat and Tilt Direction of Planesof Stacking>

Now, the relation between the direction of flow of heat in eachthermoelectric generation tube T and the tilt direction of the planes ofstacking in the thermoelectric generation tube T will be described withreference to FIGS. 16A and 16B.

FIG. 16A schematically illustrates how electric current flows in tubularthermoelectric generators T which are electrically connected together inseries. FIG. 16A schematically illustrates cross sections of three (T1to T3) of the tubular thermoelectric generators T1 to T10.

In FIG. 16A, an electrically conductive member (terminal plate) K1 isconnected to one end of the tubular thermoelectric generator T1 (e.g.,at the first electrode end), while an electrically conductive member(connection plate) J1 is connected to the other end (e.g., at the secondelectrode end) of the tubular thermoelectric generator T1. Theelectrically conductive member J1 is also connected to one end (i.e., atthe first electrode end) of the tubular thermoelectric generator T2. Asa result, the tubular thermoelectric generators T1 and T2 areelectrically connected together. Furthermore, the other end (i.e., atthe second electrode end) of the tubular thermoelectric generator T2 andone end (i.e., at the first electrode end) of the tubular thermoelectricgenerator T3 are electrically connected together via the electricallyconductive member J2.

In this case, as shown in FIG. 16A, the tilt direction of the planes ofstacking in the tubular thermoelectric generator T1 is opposite from thetilt direction of the planes of stacking in the tubular thermoelectricgenerator T2. Likewise, the tilt direction of the planes of stacking inthe tubular thermoelectric generator T2 is opposite from the tiltdirection of the planes of stacking in the tubular thermoelectricgenerator T3. That is to say, in this thermoelectric generator unit 100,each of the tubular thermoelectric generator T1 to T10 has planes ofstacking that is tilted in the opposite direction from those of anadjacent one of the tubular thermoelectric generators that is connectedto itself via a connection plate.

Suppose the hot medium HM has been brought into contact with the innerperipheral surface of each of the tubular thermoelectric generators T1to T3, and the cold medium LM has been brought into contact with theirouter peripheral surface, as shown in FIG. 16A. In that case, in thetubular thermoelectric generator T1, electric current flows from theright to the left on the paper, for example. On the other hand, in thetubular thermoelectric generator T2, of which the planes of stacking aretilted in the opposite direction from those of the tubularthermoelectric generator T1, electric current flows from the left to theright on the paper.

FIG. 17 schematically shows the directions in which electric currentflows through the two openings A61 and A62 and their surrounding region.FIG. 17 is a drawing corresponding to portion (a) of FIG. 10. In FIG.17, the flow directions of the electric current are schematicallyindicated by the dotted arrows. As shown in FIG. 17, the electriccurrent generated in the tubular thermoelectric generator T1 flowstoward the tubular thermoelectric generator T2 through the electricallyconductive ring member 56 of the opening A61, the electricallyconductive member J1 and the electrically conductive ring member 56 ofthe opening A62 in this order. The electric current that has flowed intothe tubular thermoelectric generator T2 is combined with electriccurrent generated in the tubular thermoelectric generator T2, and theelectric current thus combined flows toward the tubular thermoelectricgenerator T3. As shown in FIG. 16A, the planes of stacking of thetubular thermoelectric generator T3 are tilted in the opposite directionfrom those of the tubular thermoelectric generator T2. That is why inthe tubular thermoelectric generator T3, the electric current flows fromthe right to the left in FIG. 16A. Consequently, the electromotiveforces generated in the respective tubular thermoelectric generators T1to T3 get superposed one upon the other without canceling each other. Bysequentially connecting a plurality of tubular thermoelectric generatorsT together in this manner so that the tilt direction of their planes ofstacking inverts alternately one generator after another, an evengreater voltage can be extracted from the thermoelectric generator unit.

Next, look at FIG. 16B, which also schematically shows, just like FIG.16A, electric current flowing through tubular thermoelectric generatorsT which are electrically connected in series. As in the example shown inFIG. 16A, the tubular thermoelectric generators T1 to T3 are alsosequentially connected in FIG. 16B so that the tilt direction of theirplanes of stacking inverts alternately one generator after another. Inthis case, since the planes of stacking in one of any two adjacenttubular thermoelectric generators connected together are tilted in theopposite direction from the planes of stacking in the other tubularthermoelectric generator, the electromotive forces generated in therespective tubular thermoelectric generators T1 to T3 get superposed oneupon the other without canceling each other.

If the cold medium LM is brought into contact with the inner peripheralsurface of each of the tubular thermoelectric generators T1 to T3 andthe hot medium HM is brought into contact with their outer peripheralsurface as shown in FIG. 16B, the polarity of voltage generated in eachof the tubular thermoelectric generators T1 to T3 becomes opposite fromthe one shown in FIG. 16A. In other words, if the direction of thetemperature gradient in each tubular thermoelectric generator isinverted, then the polarity of the electromotive force in that tubularthermoelectric generator (which may also be called the direction ofelectric current flowing through that tubular thermoelectric generator)inverts. Therefore, to make electric current flow from the electricallyconductive member K1 toward the electrically conductive member J3 as inFIG. 16A, the configurations on the first and second electrode sides ineach of the tubular thermoelectric generators T1 to T3 may be oppositefrom the configurations shown in FIG. 16A. It should be noted thatelectric current flow directions shown in FIGS. 16A and 16B are justexamples. Depending on the material to make the metal layers 20 and thethermoelectric material to make the thermoelectric material layers 22,the electric current flow directions may be opposite from the ones shownin FIGS. 16A and 16B.

As already described with reference to FIGS. 16A and 16B, the polarityof the voltage generated in the tubular thermoelectric generator Tdepends on the tilt direction of the planes of stacking of that tubularthermoelectric generator T. That is why when the tubular thermoelectricgenerator T is going to be replaced, for example, the tubularthermoelectric generator T needs to be arranged appropriately with thetemperature gradient between the inner and outer peripheral surfaces ofthe tubular thermoelectric generator T in the thermoelectric generatorunit 100 taken into account.

FIGS. 18A and 18B are perspective views each illustrating an exemplarytubular thermoelectric generator, of which the electrodes haveindicators of their polarity. In the tubular thermoelectric generator Tshown in FIG. 18A, molded portions (embossed marks) Mp indicating thepolarity of the voltage generated in the tubular thermoelectricgenerator have been formed on the first and second electrodes E1 a andE2 a. On the other hand, in the tubular thermoelectric generator T shownin FIG. 18B, marks Mk indicating whether the planes of stacking in thetubular thermoelectric generator T are tilted toward the first electrodeE1 b or the second electrode E2 b are left on the first and secondelectrodes E1 b and E2 b. These molded portions (e.g., convex or concaveportions) and marks may be combined together. Optionally, these moldedportions and marks may be added to the tube body Tb or to only one ofthe first and second electrodes.

In this manner, molded portions or marks indicating the polarity of thevoltage generated in the tubular thermoelectric generator T may be addedto the first and second electrodes, for example. In that case, it can beseen quickly just from the appearance of the tubular thermoelectricgenerator T whether the planes of stacking of the tubular thermoelectricgenerator T are tilted toward the first electrode or the secondelectrode. Optionally, instead of adding such molded portions or marks,the first and second electrodes may have mutually different shapes. Forexample, the lengths, thicknesses or cross-sectional shapes as viewed ona plane that intersects with the axial direction at right angles may bedifferent from each other between the first and second electrodes.

<Electrical Connection Structure for Extracting Electric Power Out ofThermoelectric Generator Unit 100>

Now look at FIG. 5 again. In the example illustrated in FIG. 5, tentubular thermoelectric generators T1 to T10 are electrically connectedin series via electrically conductive members J1 to J9. Each of theseelectrically conductive members J1 to J9 connects its associated twotubular thermoelectric generators T together just as described above. Anexemplary electrical connection structure for extracting electric powerout of the thermoelectric generator unit 100 from the two tubulargenerators T1 and T10 located at both ends of the series circuit willnow be described.

First, look at FIG. 19, which illustrates the other side face of thethermoelectric generator unit 100 shown in FIG. 7A (left side view).While FIG. 7B shows a configuration for the plate 36, FIG. 19 shows aconfiguration for the plate 34. Any member or operation that has alreadybeen described with respect to the plate 36 will not be described allover again to avoid redundancies.

As shown in FIG. 19, each of the channels C42 to C45 interconnects atleast two of the openings A cut through the plate 34. In the presentspecification, such channels will sometimes be referred to as“interconnections” hereinbelow. The electrically conductive membershoused in these interconnections may have the same configuration as theelectrically conductive member J1. On the other hand, the channel C41 isprovided for the plate 34 so as to run from the opening A41 to the outeredge of the plate 34. In the present specification, such a channelprovided to run from an opening of a plate to its outer edge will besometimes hereinafter referred to as a “terminal connection”. Thechannels C41 and C46 shown in FIG. 19 are terminal connections. In eachterminal connection, the electrically conductive member functioning as aterminal for connecting to an external circuit is housed.

Portion (a) of FIG. 20 is a schematic partial cross-sectional view ofthe plate 34. Specifically, portion (a) of FIG. 20 schematicallyillustrates a cross section of the plate as viewed on a plane includingthe center axis of the tubular thermoelectric generator T1 andcorresponding to the plane R-R shown in FIG. 19. More specifically,portion (a) of FIG. 20 illustrates the structure of one A41 of multipleopenings A that the plate 34 has and a region surrounding it. Portion(b) of FIG. 20 illustrates the appearance of an electrically conductivemember K1 as viewed in the direction indicated by the arrow V2 inportion (a) of FIG. 20. This electrically conductive member K1 has athrough hole Kh at one end. More specifically, this electricallyconductive member K1 includes a ring portion Kr with the through hole Khand a terminal portion Kt extending outward from the ring portion Kr.Just like the electrically conductive member J1, this electricallyconductive member K1 is also typically made of a metal.

As shown in portion (a) of FIG. 20, one end of the tubularthermoelectric generator T1 (on the first electrode side) is insertedinto the opening A41 of the plate 34. In this state, the end of thetubular thermoelectric generator T1 is inserted into the through hole Khof the electrically conductive member K1. As can be seen, anelectrically conductive member J or K1 according to this embodiment canbe said to be an electrically conductive plate with at least one hole topass the tubular thermoelectric generator T through. The structure ofthe opening A410 and the region surrounding it is the same as that ofthe opening A41 and the region surrounding it except that the end of thetubular thermoelectric generator T10 is inserted into the opening A410of the plate 34.

In the example illustrated in portion (a) of FIG. 20, the first plateportion 34 a has a recess R34 which has been cut for the opening A41.This recess R34 includes a groove portion R34 t which extends from theopening A41 through the outer edge of the first plate portion 34 a. Inthis groove portion R34 t, located is the terminal portion Kt of theelectrically conductive member K1. In this example, the space defined bythe recess R34 and a recess R41 which has been cut in the second plateportion 34 b forms a channel to house the electrically conductive memberK1. As in the example illustrated in portion (a) of FIG. 10, not onlythe electrically conductive member K1 but also a first O-ring 52 a,washers 54, an electrically conductive ring member 56 and a secondO-ring 52 b are housed in the channel C41 in the example illustrated inportion (a) of FIG. 20, too. And the end of the tubular thermoelectricgenerator T1 goes through the holes of these members. The first O-ring52 a establishes sealing so as to prevent a fluid that has been suppliedinto the shell 32 from entering the channel C41. On the other hand, thesecond O-ring 52 b establishes sealing so as to prevent a fluid locatedoutside of the second plate portion 34 b from entering the channel C41.

FIG. 21 is an exploded perspective view schematically illustrating thechannel C41 to house the electrically conductive member K1 and itsvicinity. For example, a first O-ring 52 a, a washer 54, an electricallyconductive ring member 56, the electrically conductive member K1,another washer 54 and a second O-ring 52 b may be inserted into theopening A41 from outside of the container 30. The sealing surface of thesecond plate portion 34 b (i.e., the surface that faces the first plateportion 34 a) has substantially the same configuration as the sealingsurface of the second plate portion 36 b shown in FIG. 11B. Thus, byfastening the first and second plate portions 34 a and 34 b together,the second seating surface Bsb of the second plate portion 34 b pressesthe first O-ring 52 a against the seating surface Bsa of the first plateportion 34 a through the second O-ring 52 b, electrically conductivemember K1 and electrically conductive ring member 56. In this manner,the electrically conductive member K1 can be sealed from the hot andcold media.

The ring portion Kr of the electrically conductive member K1 contactswith the flat portion 56 f of the electrically conductive ring member 56inside the opening A cut through the plate 34. In this manner, theelectrically conductive member K1 is electrically connected to the outerperipheral surface at the end of the tubular thermoelectric generator Tvia the electrically conductive ring member 56. In this case, one end ofthe electrically conductive member K1 (i.e., the terminal portion Kt)sticks out of the plate 34 as shown in portion (a) of FIG. 20. Thus,that part of the terminal portion Kt that sticks out of the plate 34 mayfunction as a terminal to connect the thermoelectric generator unit toan external circuit. As shown in FIG. 21, that part of the terminalportion Kt to stick out of the plate 34 may have a ring shape. In thepresent specification, an electrically conductive member, one end ofwhich receives a tubular thermoelectric generator inserted and the otherend of which sticks out, will sometimes be referred to as a “terminalplate” hereinbelow.

As described above, in this thermoelectric generator unit 100, thetubular thermoelectric generators T1 and T10 are respectively connectedto the two terminal plates housed in the terminal connections. Inaddition, between those two terminal plates, those tubularthermoelectric generators T1 through T10 are electrically connectedtogether in series via the connection plate housed in theinterconnection of the channel. Consequently, through the two terminalplates, one end of which sticks out of the plate (34, 36), the electricpower generated by those tubular thermoelectric generators T1 to T10 canbe extracted out of this thermoelectric generator unit 100.

The arrangements of the electrically conductive ring member 56 andelectrically conductive member J, K1 may be changed appropriately insidethe channel C. In that case, the electrically conductive ring member 56and the electrically conductive member (J, K1) just need to be arrangedso that the elastic portions 56 r of the electrically conductive ringmember 56 are inserted into the through hole Jh1, Jh2 or Kh of theelectrically conductive member. Also, as mentioned above, in animplementation in which the electrically conductive ring member 56 isomitted, the end of the tubular thermoelectric generator T may beelectrically connected to the electrically conductive member K1.Optionally, part of the flat portion 56 f of the electrically conductivering member 56 may be extended and used in place of the terminal portionKt of the electrically conductive member K1. In that case, theelectrically conductive member K1 may be omitted.

In the embodiments described above, a channel C is formed by respectiverecesses cut in the first and second plate portions. However, thechannel C may also be formed by a recess which has been cut in one ofthe first and second plate portions. If the container 30 is made of ametallic material, the inside of the channel C may be coated with aninsulator to prevent the electrically conductive members (i.e., theconnection plates and the terminal plates) from becoming electricallyconductive with the container 30. For example, the plate 34 (consistingof the plate portions 34 a and 34 b) may be comprised of a body made ofa metallic material and an insulating coating which covers the surfaceof the body at least partially. Likewise, the plate 36 (consisting ofthe plate portions 36 a and 36 b) may also be comprised of a body madeof a metallic material and an insulating coating which covers thesurface of the body at least partially. If the respective surfaces ofthe recesses cut in the first and second plate portions are coated withan insulator, the insulating coating can be omitted from the surface ofthe electrically conductive member.

<Another Exemplary Structure to Establish Sealing and ElectricalConnection>

FIG. 22 is a cross-sectional view schematically illustrating anexemplary structure for separating the medium which flows in contactwith the outer peripheral surfaces of the tubular thermoelectricgenerators T from the medium which flows in contact with the innerperipheral surface of each of the tubular thermoelectric generators T1to T10 so as to prevent those media from mixing together. In the exampleillustrated in FIG. 22, a bushing 60 is inserted from outside of thecontainer 30, thereby separating the hot and cold media from each otherand electrically connecting the tubular thermoelectric generator and theelectrically conductive member together.

In the example illustrated in FIG. 22, the opening A41 cut through theplate 34 u has an internal thread portion Th34. More specifically, thewall surface of the recess R34 that has been cut with respect to theopening A41 of the plate 34 u has the thread. The busing 60 with anexternal thread portion Th60 is inserted into the recess R34. Thebushing 60 has a through hole 60 a that runs in the axial direction. Inthis case, the end of the tubular thermoelectric generator T1 has beeninserted into the opening A41 of the plate 34 u. That is why when thebusing 60 is inserted into the recess R34, the through hole 60 acommunicates with the internal flow path of the tubular thermoelectricgenerator T1.

Inside the space left between the recess R34 and the busing 60, arrangedare various members to establish sealing and electrical connection. Inthe example illustrated in FIG. 22, an O-ring 52, the electricallyconductive member K1 and the electrically conductive ring member 56 arearranged in this order from the seating surface Bsa of the plate 34 utoward the outside of the container 30. The end of the tubularthermoelectric generator T1 is inserted into the respective holes ofthese members. The O-ring 52 contacts with the seating surface Bsa ofthe plate 34 u and the outer peripheral surface at the end of thetubular thermoelectric generator T1. In this case, when the externalthread portion Th60 is inserted into the internal thread portion Th34,the external thread portion Th60 presses the O-ring 52 against theseating surface Bsa via the flat portion 56 f of the electricallyconductive ring member 56 and the electrically conductive member K1. Asa result, sealing can be established so as to prevent the fluid suppliedinto the shell 32 and the fluid supplied into the internal flow path ofthe tubular thermoelectric generator T1 from mixing with each other. Inaddition, since the outer peripheral surface of the tubularthermoelectric generator T1 contacts with the elastic portions 56 r ofthe electrically conductive ring member 56 and since the flat portion 56f of the electrically conductive ring member 56 contacts with the ringportion Kr of the electrically conductive member K1, the tubularthermoelectric generator and the electrically conductive member can beelectrically connected together.

As can be seen, by using the members shown in FIG. 22, the hot and coldmedia can be separated from each other and the tubular thermoelectricgenerator and the electrically conductive member can be electricallyconnected together with a simpler configuration.

FIGS. 23A and 23B are cross-sectional views schematically illustratingtwo other exemplary structures for separating the hot and cold mediafrom each other and electrically connecting the tubular thermoelectricgenerator and the electrically conductive member together. Specifically,in the example shown in FIG. 23A, a first O-ring 52 a, a washer 54, theelectrically conductive ring member 56, the electrically conductivemember K1, another washer 54 and a second O-ring 52 b are arranged inthis order from the seating surface Bsa of the plate 34 u toward theoutside of the container 30. In the example illustrated in FIG. 23A, theexternal thread portion Th60 presses the O-ring 52 a against the seatingsurface Bsa via the electrically conductive member K1 and the flatportion 56 f of the electrically conductive ring member 56. On the otherhand, in the example shown in FIG. 23B, a first O-ring 52 a, theelectrically conductive member K1, the electrically conductive ringmember 56 and a second O-ring 52 b are arranged in this order from theseating surface Bsa of the plate 34 u toward the outside of thecontainer 30. In addition, in FIG. 23B, another busing 64 with a throughhole 64 a has been inserted into the through hole 60 a of the busing 60.The through hole 64 a also communicates with the internal flow path ofthe tubular thermoelectric generator T1. In the example illustrated inFIG. 23B, the external thread portion Th64 of the busing 64 presses thesecond O-ring 52 b against the seating surface Bsa. Sealing from both ofthe fluids (the hot and cold media) can be established by arranging thefirst and second O-rings 52 a and 52 b in this manner. By establishingsealing from both of the fluids (the hot and cold media), corrosion ofthe electrically conductive ring member 56 can be minimized.

As described above, one end of the terminal portion Kt of theelectrically conductive member K1 sticks out of the plate 34 u and canfunction as a terminal to connect the thermoelectric generator unit toan external circuit. In the implementations shown in FIGS. 22, 23A and23B, the electrically conductive member K1 (terminal plate) may bereplaced with a connection plate such as the electrically conductivemember J1. In that case, the end of the tubular thermoelectric generatorT1 is inserted into the through hole Jh1. If necessary, a washer 54 maybe arranged between the O-ring and the electrically conductive member,for example.

<Embodiment of Thermoelectric Generator System>

Next, an embodiment of a thermoelectric generator system according tothe present disclosure will be described.

FIG. 24A illustrates an embodiment of a thermoelectric generator systemaccording to the present disclosure. FIG. 24B is a cross-sectional viewof the system as viewed on the plane B-B shown in FIG. 24A. And FIG. 24Cis a perspective view illustrating an exemplary configuration for abuffer vessel that the thermoelectric generator system shown in FIG. 24Ahas. In FIG. 24A, the bold solid arrows generally indicate the flowdirection of the medium in contact with the outer peripheral surface ofa tubular thermoelectric generator (i.e., the medium flowing inside ofthe container 30 (and outside of the tubular thermoelectric generator)).On the other hand, the bold dashed arrows generally indicate the flowdirection of the medium in contact with the inner peripheral surface ofa tubular thermoelectric generator (i.e., the medium flowing through thethrough hole (i.e., the inner flow path) of the tubular thermoelectricgenerator). In the present specification, a path communicating with thefluid inlet and outlet ports of each container 30 will sometimes bereferred to as a “first medium path” and a path encompassing the flowpath of each tubular thermoelectric generator will sometimes be referredto as a “second medium path” hereinbelow.

The thermoelectric generator system 200A shown in FIG. 24A includesfirst and second thermoelectric generator units 100-1 and 100-2, each ofwhich has the same configuration as the thermoelectric generator unit100 described above. This thermoelectric generator system 200A furtherincludes a thick circular cylindrical buffer vessel 44 which is arrangedbetween the first and second thermoelectric generator units 100-1 and100-2. This buffer vessel 44 has a first opening 44 a 1 communicatingwith the respective flow paths of multiple tubular thermoelectricgenerators in the first thermoelectric generator unit 100-1 and a secondopening 44 a 2 communicating with the respective flow paths of multipletubular thermoelectric generators in the second thermoelectric generatorunit 100-2.

In this thermoelectric generator system 200A, the medium that has beenintroduced through the fluid inlet port 38 a 1 of the firstthermoelectric generator unit 100-1 sequentially flows through thecontainer 30 of the first thermoelectric generator unit 100-1, the fluidoutlet port 38 b 1 of the first thermoelectric generator unit 100-1, aconduit 40, the fluid inlet port 38 a 2 of the second thermoelectricgenerator unit 100-2 and the container 30 of the second thermoelectricgenerator unit 100-2 in this order to reach a fluid outlet port 38 b 2(which is the first medium path). That is to say, the medium that hasbeen supplied into the container 30 of the first thermoelectricgenerator unit 100-1 is supplied to the inside of the container 30 ofthe second thermoelectric generator unit 100-2 through the conduit 40.It should be noted that this conduit 40 does not have to be a straightone but may be a bent one, too.

On the other hand, the internal flow paths of the multiple tubularthermoelectric generators in the first thermoelectric generator unit100-1 communicate with the internal flow paths of the multiple tubularthermoelectric generators in the second thermoelectric generator unit100-2 through the first and second openings 44 a 1 and 44 a 2 of thebuffer vessel 44 (which is the second medium path). The medium that hasbeen introduced into the respective internal flow paths of the multipletubular thermoelectric generators in the first thermoelectric generatorunit 100-1 is confluent with each other in the buffer vessel 44 and thenintroduced into the respective internal flow paths of the multipletubular thermoelectric generators in the second thermoelectric generatorunit 100-2.

In a thermoelectric generator system including a plurality ofthermoelectric generator units, the second medium path encompassing theflow paths of the respective tubular thermoelectric generators may bedesigned arbitrarily. Note that the degree of heat exchange to becarried out in a single container 30 via multiple tubular thermoelectricgenerators may vary from one generator to another. For this reason,between two adjacent thermoelectric generator units, if the internalflow paths of the respective tubular thermoelectric generators in onethermoelectric generator unit are connected in series to the internalflow paths of the respective tubular thermoelectric generators in theother thermoelectric generator unit, the temperature of the mediumflowing through the internal flow paths will vary even more. Withincreased variations in the temperature of the medium among the internalflow paths of the respective tubular thermoelectric generators, thepower output levels of the respective tubular thermoelectric generatorsmay also vary from one generator to another.

For example, if the tubular thermoelectric generators are electricallyconnected in series together in each thermoelectric generator unit,electric power can be generated efficiently by reducing a variation inpower output level between the respective tubular thermoelectricgenerators. Particularly when a plurality of thermoelectric generatorunits are electrically connected in series together, electric power canbe generated even more efficiently by reducing a variation in poweroutput level between those thermoelectric generator units.

In this thermoelectric generator system 200A, the medium that has flowedthrough the respective internal flow paths of the multiple tubularthermoelectric generators in the first thermoelectric generator unit100-1 into the buffer vessel 44 exchanges heat in the buffer vessel 44and then is supplied to the internal flow paths of the multiple tubularthermoelectric generators in the second thermoelectric generator unit100-2. Since the medium that has flowed through the internal flow pathsof the multiple tubular thermoelectric generators in the firstthermoelectric generator unit 100-1 into the buffer vessel 44 exchangesheat in the buffer vessel 44, the temperature of the medium can be moreuniform. By mixing the medium flowing through the internal flow path ofone tubular thermoelectric generator with the medium flowing through theinternal flow path of another tubular thermoelectric generator in thismanner, the temperature of the media flowing through the respectiveinternal flow paths of multiple tubular thermoelectric generators can bemade more uniform, which is advantageous.

In the example illustrated in FIG. 24A, the second medium path isdesigned so that the fluid flows in the same direction through therespective flow paths of multiple tubular thermoelectric generators T.However, the flow direction of the fluid through the flow paths ofmultiple tubular thermoelectric generators T does not have to be thesame direction. Alternatively, the flow direction of the fluid throughthe flow paths of multiple tubular thermoelectric generators T may alsobe set in various manners according to the design of the flow paths ofthe hot and cold media. Also, in the thermoelectric generator system ofthe present disclosure, multiple thermoelectric generator units may beconnected either in series to each other or parallel with each other.

<Another Embodiment of Thermoelectric Generator System>

FIG. 25A illustrates another embodiment of a thermoelectric generatorsystem according to the present disclosure. FIG. 25B is across-sectional view of the system as viewed on the plane B-B shown inFIG. 25A. And FIG. 25C is a cross-sectional view of the system as viewedon the plane C-C shown in FIG. 25A.

In the thermoelectric generator system 200B of this embodiment, thebuffer vessel 44 has two baffle plates 46 a and 46 b inside. A number ofrectangular openings are cut through one of these two baffle plates 46 aor 46 b, and a number of rectangular openings are also cut through theother baffle plate 46 b or 46 a, the distribution pattern of rectangularopenings being dissimilar between the two baffle plates 46 a and 46 b(see FIGS. 25B and 25C). The medium flowing inside the buffer vessel 44passes through those openings cut through each of the two baffle plates46 a, 46 b, whereby a turbulent flow is generated and a stirring effectemerges to promote uniformity of the temperature of the medium. In thismanner, the buffer vessel 44 may have such a baffle structure fordisturbing the flow of the fluid that has flowed into the buffer vessel44 through the respective flow paths of those tubular thermoelectricgenerators.

The baffle plates 46 a, 46 b just need to have such a shape as to atleast partially change the flow direction of the fluid. That is why theshape, size and locations of those openings cut through the baffleplates 46 a, 46 b do not have to be the exemplary ones illustrated inFIGS. 25B and 25C but may also be arbitrary ones. Each of those baffleplates may be divided into multiple pieces. Each of those openings maybe a slit. Any arbitrary number of baffle plates may be provided. Forexample, the stirring effect can also be achieved with only one baffleplate. The baffle plate does not need to have a flat plate shape but mayalso have a helical, radial or grid shape.

FIG. 26A illustrates still another embodiment of a thermoelectricgenerator system according to the present disclosure. FIG. 26B is across-sectional view of the system as viewed on the plane B-B shown inFIG. 26A.

In the exemplary configuration shown in FIGS. 26A and 26B, a baffle 46 cwith a three-dimensional shape is provided for the buffer vessel 44 ofthe thermoelectric generator system 200F. In the example illustrated inFIGS. 26A and 26B, the baffle 46 c is arranged around the center of thebuffer vessel 44 on a cross section which intersects at right angleswith the flow direction of the fluid that has flowed into the buffervessel 44. As a result, a gap G is left between the inner wall 45 of thebuffer vessel 44 and the outer edge of the baffle 46 c. The fluid thathas flowed into the buffer vessel 44 passes through this gap G and thenis introduced into the respective internal flow paths of the tubularthermoelectric generators of the thermoelectric generator unit (e.g.,the second thermoelectric generator unit 100-2). It should be noted thatthe baffle 46 c may be supported inside the buffer vessel 44 by asupporting member arranged between the baffle 46 c and the inner wall 45of the buffer vessel 44. However, illustration of such a supportingmember is omitted in FIGS. 26A and 26B.

As schematically shown in FIG. 24A, the fluid flowing through the secondmedium path goes from the left toward the right in FIG. 26A, forexample. In the example illustrated in FIG. 26A, the baffle 46 c hassuch a shape as to change the flow direction of the fluid flowing aroundthe center of the buffer vessel 44 so that the fluid goes outward fromthe center of the buffer vessel 44. For example, the baffle 46 c mayhave a shape which expands gradually in the flow direction of the fluidas shown in FIG. 26A. In the example illustrated in FIG. 26A, the baffle46 c has a circular cone shape.

In the configuration illustrated in FIGS. 26A and 26B, while the fluidflows into the buffer vessel 44 from the first thermoelectric generatorunit 100-1, the portion of the fluid flowing around the center of thebuffer vessel 44 collides against the baffle 46 c existing near thecenter of the buffer vessel 44. The fluid flowing around the center ofthe buffer vessel 44 has its flow direction changed by colliding againstthe baffle 46 c, passes through the gap G and then goes toward thesecond thermoelectric generator unit 100-2. Meanwhile, another part ofthe fluid that has flowed into the buffer vessel 44 flows around theinner wall 45, passes through the gap G and then goes toward the secondthermoelectric generator unit 100-2. That is to say, both the fluidflowing around the center of the buffer vessel 44 and the fluid flowingaround the inner wall 45 pass through the gap G. In such a situation,the medium temperature can be made even more uniform by mixing thesefluids together.

As described above, in a thermoelectric generator unit including aplurality of tubular thermoelectric generators, the degree of heatexchange carried out by those tubular thermoelectric generators variesaccording to the position of a tubular thermoelectric generator in thecontainer 30. This will be described by taking, as an example, asituation where the temperature of a medium flowing through the firstmedium path is lower than that of a medium flowing through the secondmedium path.

The temperature of the medium (hot medium) flowing inside the tubularthermoelectric generators of the first thermoelectric generator unit100-1 decreases as the medium goes farther inside the tubularthermoelectric generators as a result of heat exchange with the medium(cold medium) supplied through the fluid inlet port of the container 30and flowing through the first medium path. In the exemplaryconfiguration described above, the cold medium is introduced through theside surface of the container 30 and some of the multiple tubularthermoelectric generators is arranged so as to be surrounded with theother tubular thermoelectric generators in a single thermoelectricgenerator unit. For example, in the configuration shown in FIG. 3B,among the ten tubular thermoelectric generators T1 through T10, thetubular thermoelectric generators T6 and T8 arranged around the centerof the container 30 are surrounded with the other tubular thermoelectricgenerators T1 to T5, T7, T9 and T10. That is why a decrease in thetemperature of the medium flowing inside the tubular thermoelectricgenerators T6 and T8 tends to be less significant than a decrease in thetemperature of the medium flowing inside the tubular thermoelectricgenerators that are arranged near the inner wall of the container 30.That is to say, in the fluid that has flowed into the buffer vessel 44,a part of the fluid flowing around the center of the buffer vessel 44sometimes has a higher temperature than another part of the fluidflowing around the inner wall 45. Consequently, the medium flowing intothe buffer vessel 44 from the first thermoelectric generator unit 100-1may have a temperature distribution in which the temperature gets higherthe closer to the center of the first opening 44 a 1 and gets lower thecloser to the periphery.

As can be seen from the foregoing description, by providing, inside thebuffer vessel 44, a mechanism for making a medium that has flowed inthrough the center of the first opening 44 a 1 go toward the periphery,the temperature of the medium in the buffer vessel 44 can be madeuniform more efficiently. For example, by providing a baffle 46 c suchas the one shown in FIGS. 26A and 26B inside the buffer vessel 44, thetemperature of the medium inside the buffer vessel 44 can be madeuniform more efficiently and variation in power output level between therespective tubular thermoelectric generators can be reduced. A structuresuch as the baffle may be any mechanism as long as it can guide themedium flowing around the center of the buffer vessel 44 toward theperiphery. The baffle does not need to have a circular cone shape suchas the one shown in FIGS. 26A and 26B but may also have a triangularpyramid, quadrangular pyramid or any other pyramid shape or a sphericalshape as well.

Optionally, from the standpoint of making the temperature of the mediumas uniform as possible inside the buffer vessel 44, a structure havingsuch a shape as to change the flow direction of the fluid flowing aroundthe peripheral area inside the buffer vessel 44 so that the fluid goestoward the center of the buffer vessel 44 may be provided for the buffervessel 44. Even if such a configuration is adopted, the temperature ofthe medium can also be made more uniform by mixing together the fluidflowing around the center of the buffer vessel 44 and the fluid flowingaround the inner wall 45 of the buffer vessel 44.

For example, the buffer vessel 44 may have, as such a structure fordisturbing the flow of the fluid that has flowed into the buffer vessel44, projections on the inner wall 45. The projections are arranged so asto project toward the center of the buffer vessel 44. The arrangement,number and size of the projections may be determined appropriately. Forexample, the projections may be baffles or fins which either form partsof the inner wall 45 or have been formed separately from the inner wall45. The shape of the projections is not particularly limited and doesnot have to be a flat plate shape. The surface of the projections may ormay not be connected smoothly to the surface of the inner wall 45.

By providing such projections that project toward the center of thebuffer vessel 44, an aperture, of which the area is smaller than that ofthe first opening 44 a 1, may be formed around the center of the buffervessel 44. In the fluid that has flowed into the buffer vessel 44, ifthe fluid flowing around the inner wall 45 of the buffer vessel 44 isguided by those projections toward such an aperture and is mixed withthe fluid flowing around the center of the buffer vessel 44, thetemperature of the medium can be made even more uniform.

As long as it can achieve the effect of making the temperaturedistribution uniform by stirring up the medium, any structure other thanthe one described above may either be provided inside of the buffervessel or form part of the buffer vessel. For example, the inner wall ofthe buffer vessel 44 may have unevenness or grooves. Alternatively, thebuffer vessel 44 may be narrowed in the middle. Still alternatively, astructure having such a shape as to change the flow direction of thefluid flowing around the center of the buffer vessel 44 so that thefluid goes outward from the center and a structure having such a shapeas to change the flow direction of the fluid flowing around theperiphery so that the fluid goes toward the center may be used incombination.

FIG. 27A illustrates yet another embodiment of a thermoelectricgenerator system according to the present disclosure. FIG. 27B is across-sectional view of the system as viewed on the plane B-B shown inFIG. 27A.

The structure arranged inside the buffer vessel 44 may include a movableportion to change at least partially the flow direction of the fluidthat has flowed into the buffer vessel 44. In the thermoelectricgenerator system 200C of this embodiment, the buffer vessel 44 hasblades 48 which rotate internally. Those blades 48 are supportedrotatably by a supporting member (not shown) and rotated by the mediumflow. Optionally, the blades 48 may be driven by an external power unitsuch as a motor. In any case, as the blades 48 rotate, a turbulent flowis generated and the stirring effect is produced to make the temperatureof the medium even more uniform. Even when fixed so as not to rotate,those blades 48 also disturb the medium flow as much as the baffle, thusalso making the medium temperature more uniform. If necessary, multiplesets of blades 48 (or propellers) may be provided inside the buffervessel 44.

In place of, or in addition to, the blades 48, any other stirringmechanism which gets rotated, swung or deformed by the medium flow maybe provided inside the buffer vessel 44 as well.

FIG. 28A illustrates yet another embodiment of a thermoelectricgenerator system according to the present disclosure. FIG. 28B is across-sectional view of the system as viewed on the plane B-B shown inFIG. 28A.

In the thermoelectric generator system 200D of this embodiment, thebuffer vessel 44 has a partition 47 c inside. Thus, the space inside ofthe buffer vessel 44 is divided into two spaces 44A and 44B. Forexample, as shown in FIG. 28B, the space 44A communicates with half ofthe openings A cut through the container of the second thermoelectricgenerator unit 100-2. On the other hand, the space 44B communicates withthe other half of the openings A cut through the container of the secondthermoelectric generator unit 100-2.

In this thermoelectric generator system 200D, part of the medium flowsinto the space 44A inside the buffer vessel 44 from a half of thetubular thermoelectric generators in the first thermoelectric generatorunit 100-1. The rest of the medium flows into the space 44B from theother half of the tubular thermoelectric generators in the firstthermoelectric generator unit 100-1. In each of these two spaces 44A and44B created inside the buffer vessel 44, the medium that has flowed infrom the respective internal flow paths of the tubular thermoelectricgenerators of the first thermoelectric generator unit 100-1 is subjectedto heat exchange. In this manner, the inside of the buffer vessel 44 maybe divided into multiple spaces and the medium that has flowed into thebuffer vessel 44 may be subjected to heat exchange in each of thosedivided spaces.

The shape, number and arrangement of the partition 47 c do not have tobe the ones shown in FIGS. 28A and 28B but may be determinedarbitrarily. If three or more thermoelectric generator units areconnected together in series, the shape, number or arrangement of thepartitions 47 c may be changed from one buffer vessel inserted betweentwo adjacent ones of the thermoelectric generator unit to another. Inthat case, the medium temperature can be made even more uniform.

Optionally, the baffles (e.g., baffle plates), stirring mechanism, andpartitions that have been described with reference to FIGS. 25A through28B may be used in combination. If three or more thermoelectricgenerator units are connected together in series, the buffer vessel 44may be inserted either between each pair of two adjacent thermoelectricgenerator units or between only some pair(s) of two adjacentthermoelectric generator units.

Alternatively, the baffles, stirring mechanism and partitions may beprovided inside the container 30. For example, when the hot medium flowsthrough the internal flow paths of the tubular thermoelectricgenerators, the cold medium flows inside the container 30. The coldmedium is heated by the tubular thermoelectric generators in thecontainer 30 to have its temperature raised locally. However, thetemperature of the cold medium remains relatively low distant from thetubular thermoelectric generators. That is why if the flow of the coldmedium is disturbed inside the container 30 by the baffles or stirringmechanism, the temperature distribution of the cold medium can be mademore uniform, and the temperature of the cold medium can be lowered in aregion where the cold medium is in contact with the tubularthermoelectric generators.

Next, look at FIG. 29, which illustrates still another exemplaryconfiguration for a thermoelectric generator system according to thepresent disclosure. In FIG. 29, the bold solid arrows generally indicatethe flow direction of the medium in contact with the outer peripheralsurface of a tubular thermoelectric generator. On the other hand, thebold dashed arrows generally indicate the flow direction of the mediumin contact with the inner peripheral surface of the tubularthermoelectric generator as in FIG. 24A. This thermoelectric generatorsystem 200E is configured so that the flow direction of the fluidflowing through the respective flow paths of the multiple tubularthermoelectric generators T in the first thermoelectric generator unit100-1 is anti-parallel to that of the fluid flowing through therespective flow paths of the multiple tubular thermoelectric generatorsT in the second thermoelectric generator unit 100-2.

In this thermoelectric generator system 200E, the first and secondthermoelectric generator units 100-1 and 100-2 are arranged spatiallyparallel with each other. For example, the second thermoelectricgenerator unit 100-2 may be arranged by the first thermoelectricgenerator unit 100-1. Optionally, the first and second thermoelectricgenerator units 100-1 and 100-2 may be vertically stacked one upon theother. In that case, the medium will flow vertically through the firstmedium path.

As shown in FIG. 29, the buffer vessel 44 may have a bent shape. As canbe seen, in a thermoelectric generator system according to the presentdisclosure, the flow paths for hot and cold media may be designed invarious manners. For example, the flow paths may be designed flexiblyaccording to the area of the place where the thermoelectric generatorsystem needs to be installed. The arrangements shown in FIGS. 24Athrough 29 are just examples. Rather the first medium path communicatingwith the fluid inlet and outlet ports of each container and the secondmedium path encompassing the respective flow paths of the tubularthermoelectric generators may be designed arbitrarily. Also, thosethermoelectric generator units may be electrically connected either inseries to each other or parallel with each other.

<Exemplary Configuration for Thermoelectric Generator System's ElectricCircuit>

Next, an exemplary configuration for an electric circuit that thethermoelectric generator system according to the present disclosure mayinclude will be described with reference to FIG. 30.

In the example shown in FIG. 30, the thermoelectric generator system 200according to this embodiment includes an electric circuit 250 whichreceives electric power from the thermoelectric generator units 100-1,100-2. That is to say, in one implementation, the plurality ofelectrically conductive members may have an electric circuit which iselectrically connected to the plurality of tubular thermoelectricgenerators.

The electric circuit 250 includes a boost converter 252 which boosts thevoltage of the electric power supplied from the thermoelectric generatorunits 100-1, 100-2, and an inverter (DC-AC inverter) 254 which convertsthe DC power supplied from the boost converter 252 into AC power (ofwhich the frequency may be 50/60 Hz, for example, but may also be anyother frequency). The AC power may be supplied from the inverter 254 toa load 400. The load 400 may be any of various electrical or electronicdevices that operate using AC power. The load 400 may have a chargingfunction in itself, and does not have to be fixed to the electriccircuit 250. Any AC power that has not been dissipated by the load 400may be connected to a commercial grid 410 so that the electricity can besold.

The electric circuit 250 in the example shown in FIG. 30 includes acharge-discharge control section 262 and an accumulator 264 for storingthe DC power obtained from the thermoelectric generator units 100-1,100-2. The accumulator 264 may be a chemical battery such as a lithiumion secondary battery, or a capacitor such as an electric double-layercapacitor, for example. The electric power stored in the accumulator 264may be fed as needed to the boost converter 252 by the charge-dischargecontrol section 262, and may be used or sold as AC power via theinverter 254.

The magnitude of the electric power supplied from the thermoelectricgenerator unit 100-1, 100-2 may vary with time either periodically orirregularly. For example, if the heat source of the hot medium is thewaste heat discharged from a factory, the temperature of the hot mediummay vary according to the operating schedule of that factory. In thatcase, the power generation state of the thermoelectric generator unit100-1, 100-2 will vary so significantly that the voltage of the electricpower and/or the amount of electric current supplied from thethermoelectric generator unit 100-1, 100-2 will vary, too. However, evenif the power generation state varies in this manner, the thermoelectricgenerator system 200 shown in FIG. 30 can also minimize the influencecaused by such a variation in power output level by making thecharge-discharge control section 262 accumulate electric power in theaccumulator 264.

If the electric power generated is dissipated in real time, then thevoltage step-up ratio of the boost converter 252 may be adjustedaccording to the variation in power generation state. Alternatively, acontrol operation may also be carried out so that the power generationstate is maintained in steady state by regulating the flow rate,temperature and other parameters of the hot or cold medium to besupplied to the thermoelectric generator unit 100-1, 100-2 with such avariation in power generation state sensed or predicted.

Now take a look at FIG. 4 again. In the system illustrated in FIG. 4,the flow rate of the hot medium may be adjusted by the pump P1. In thesame way, the flow rate of the cold medium may be adjusted by the pumpP2. By adjusting the flow rate(s) of one or both of the hot and coldmedia, the power output level of the tubular thermoelectric generatorcan be controlled.

Optionally, the temperature of the hot medium may be controlled byadjusting the quantity of heat supplied from a high-temperature heatsource (not shown) to the hot medium. In the same way, the temperatureof the cold medium may also be controlled by adjusting the quantity ofheat dissipated from the cold medium into a low-temperature heat source(not shown, either).

Although not shown in FIG. 4, the flow rates of the respective mediasupplied to the thermoelectric generator system may be adjusted byproviding a valve and a branch path for at least one of the flow pathsof the hot and cold media.

<Another Embodiment of Thermoelectric Generator System>

Another embodiment of a thermoelectric generator system according to thepresent disclosure will now be described with reference to FIG. 31.

In this embodiment, a thermoelectric generator unit (such as thethermoelectric generator unit 100-1, 100-2) is provided for a generalwaste disposal facility (that is a so-called “garbage disposal facility”or a “clean center”). In recent years, at a waste disposal facility,high-temperature, high-pressure steam (at a temperature of 400 to 500degrees Celsius and at a pressure of several MPa) is sometimes generatedfrom the thermal energy produced when garbage (waste) is incinerated.Such steam energy is converted into electricity by turbine generator andthe electricity thus generated is used to operate the equipment in thefacility.

The thermoelectric generator system 300 of this embodiment includes aplurality of thermoelectric generator units. In the example illustratedin FIG. 31, the hot medium supplied to the thermoelectric generatorunits 100-1 and 100-2 has been produced based on the heat of combustiongenerated at the waste disposal facility. More specifically, this systemincludes an incinerator 310, a boiler 320 to produce high-temperature,high-pressure steam based on the heat of combustion generated by theincinerator 310, and a turbine 330 which is driven by thehigh-temperature, high-pressure steam produced by the boiler 320. Theenergy generated by the turbine 330 driven is given to a synchronousgenerator (not shown), which converts the energy into AC power (such asthree-phase AC power).

The steam that has been used to drive the turbine 330 is turned back bya condenser 360 into liquid water, which is then supplied by a pump 370to the boiler 320. This water is a working medium that circulatesthrough a “heat cycle” formed by the boiler 320, turbine 330 andcondenser 360. Part of the heat given by the boiler 320 to the waterdoes work to drive the turbine 330 and then is given by the condenser360 to cooling water. In general, cooling water circulates between thecondenser 360 and a cooling tower 350 as indicated by the dotted arrowsin FIG. 31.

As can be seen, only a part of the heat generated by the incinerator 310is converted by the turbine 330 into electricity, and the thermal energythat the low-temperature, low-pressure steam has after the turbine 330has been driven has not been converted into, and used as, electricalenergy but often just dumped into the ambient according to conventionaltechnologies. According to this embodiment, however, the low-temperaturesteam or hot water that has done work to drive the turbine 330 can beused effectively as a heat source for the hot medium. In thisembodiment, heat is obtained by the heat exchanger 340 from the steam atsuch a low temperature (of 140 degrees Celsius, for example) and hotwater at 99 degrees Celsius is obtained, for example. And this hot wateris supplied as hot medium to the thermoelectric generator units 100-1,100-2.

On the other hand, a part of the cooling water used at a waste disposalfacility, for example, may be used as the cold medium. If the wastedisposal facility has the cooling tower 350, water at about 10 degreesCelsius can be obtained from the cooling tower 350 and used as the coldmedium. Alternatively, the cold medium does not have to be obtained froma special cooling tower but may also be well water or river water insidethe facility or in the neighborhood.

The thermoelectric generator units 100-1, 100-2 shown in FIG. 31 may beconnected to the electric circuit 250 shown in FIG. 30, for example. Theelectricity generated by the thermoelectric generator units 100-1, 100-2may be either used in the facility or accumulated in the accumulator264. The extra electric power may be converted into AC power and thensold through the commercial grid 410.

The thermoelectric generator system 300 shown in FIG. 31 has aconfiguration in which a plurality of thermoelectric generator units areincorporated into the waste heat utilization system of a waste disposalfacility including the boiler 320 and the turbine 330. However, tooperate the thermoelectric generator units 100-1, 100-2, the boiler 320,turbine 330, condenser 360 and heat exchanger 340 are not indispensablemembers. If there is any gas or hot water at a relatively lowtemperature which has been just disposed of according to conventionaltechnologies, that gas or water may be effectively used as hot mediumdirectly. Or another gas or liquid may be heated by a heat exchanger andused as a hot medium. The system shown in FIG. 31 is just one of manypractical examples.

As is clear from the foregoing description of embodiments, an embodimentof a thermoelectric generator system according to the present disclosurecan collect and utilize effectively such thermal energy that has beenjust dumped unused into the ambient according to conventionaltechnologies. For example, by generating a high-temperature medium basedon the heat of combustion of garbage at a waste disposal facility, thethermal energy of a gas or hot water at a relatively low temperaturethat has been just disposed of according to conventional technologiescan be utilized effectively.

A thermoelectric generator system according to one aspect of the presentdisclosure comprises a plurality of thermoelectric generator unitsincluding first and second thermoelectric generator units. Each of thefirst and second thermoelectric generator units includes a plurality oftubular thermoelectric generators. Each of the plurality of tubularthermoelectric generators may have an outer peripheral surface, an innerperipheral surface and a flow path defined by the inner peripheralsurface, and may generate electromotive force in an axial direction ofeach said tubular thermoelectric generator based on a difference intemperature between the inner and outer peripheral surfaces. Each of thefirst and second thermoelectric generator units may further include: acontainer housing the plurality of tubular thermoelectric generatorsinside, the container having fluid inlet and outlet ports through whicha fluid flows inside the container, and a plurality of openings intowhich the respective tubular thermoelectric generators are inserted; anda plurality of electrically conductive members providing electricalinterconnection for the plurality of tubular thermoelectric generators.The thermoelectric generator system may further include a buffer vesselwhich is arranged between the first and second thermoelectric generatorunits. The buffer vessel may have a first opening communicating with therespective flow paths of the plurality of tubular thermoelectricgenerators in the first thermoelectric generator unit and a secondopening communicating with the respective flow paths of the plurality oftubular thermoelectric generators in the second thermoelectric generatorunit.

In one embodiment, the buffer vessel contains a baffle structuretherein.

In one embodiment, the structure is shaped to change at least partiallythe flow direction of a fluid flowing into the buffer vessel through therespective flow paths of the plurality of tubular thermoelectricgenerators of an upstream one of the first and second thermoelectricgenerator units.

In one embodiment, the structure includes at least one baffle plate.

In one embodiment, the structure has a movable portion.

In one embodiment, the structure is shaped to change the flow directionof the fluid flowing around a cross-sectional center of the buffervessel so that the fluid goes outward from the cross-sectional center ofthe buffer vessel.

In one embodiment, the structure is shaped to expand gradually in theflow direction of the fluid.

In one embodiment, a gap is left between an inner wall of the buffervessel and an outer edge of the structure.

In one embodiment, the structure is shaped to change the flow directionof the fluid flowing around an inner periphery of the buffer vessel sothat the fluid goes toward a cross-sectional center of the buffervessel.

In one embodiment, the structure is a projection which is provided onthe inner wall of the buffer vessel so as to project toward across-sectional center of the buffer vessel.

In one embodiment, the container includes: a shell surrounding theplurality of tubular thermoelectric generators; and a pair of plates.Each of the pair of plates is fixed to the shell and at least one of thepair of plates has a plurality of openings and channels. Each channelhouse an electrically conductive member. The respective ends of thetubular thermoelectric generators may be inserted into the plurality ofopenings of the plates, and at least one of the channels may have aninterconnection which connects at least two of the plurality of openingstogether.

Any of the aforementioned thermoelectric generator systems may include:a first medium path communicating with the fluid inlet and outlet portsof the container in the first thermoelectric generator unit and thefluid inlet and outlet ports of the container in the secondthermoelectric generator unit; and a second medium path encompassing therespective flow paths of the plurality of tubular thermoelectricgenerators in the first and second thermoelectric generator units.

In one embodiment, in the second medium path, the fluid flows in thesame direction through the respective flow paths of the plurality oftubular thermoelectric generators.

In one embodiment, the plurality of electrically conductive membersconnect the plurality of tubular thermoelectric generators electricallyin series together.

The thermoelectric generator system may further comprise an electriccircuit electrically connected to the plurality of tubularthermoelectric generators via at least one of the plurality ofelectrically conductive members.

In one embodiment, the first and second thermoelectric generator unitsare electrically connected in series together.

A thermoelectric generator system according to another aspect of thepresent disclosure comprises a plurality of thermoelectric generatorunits including first and second thermoelectric generator units. Each ofthe first and second thermoelectric generator units includes a pluralityof tubular thermoelectric generators. Each of the plurality of tubularthermoelectric generators may have an outer peripheral surface, an innerperipheral surface and a flow path defined by the inner peripheralsurface, and may generate electromotive force in an axial direction ofeach said tubular thermoelectric generator based on a difference intemperature between the inner and outer peripheral surfaces. Each of thefirst and second thermoelectric generator units may further include: acontainer housing the plurality of tubular thermoelectric generatorsinside, the container having fluid inlet and outlet ports through whicha fluid flows inside the container, and a plurality of openings intowhich the respective tubular thermoelectric generators are inserted; anda plurality of electrically conductive members providing electricalinterconnection for the plurality of tubular thermoelectric generatorsin series. The first and second thermoelectric generator units may beelectrically connected in series together. The thermoelectric generatorsystem further may include a buffer vessel which is arranged between thefirst and second thermoelectric generator units. The buffer vessel mayhave a first opening communicating with the respective flow paths of theplurality of tubular thermoelectric generators in the firstthermoelectric generator unit and a second opening communicating withthe respective flow paths of the plurality of tubular thermoelectricgenerators in the second thermoelectric generator unit. Thethermoelectric generator system may further include a medium pathencompassing the respective flow paths of the tubular thermoelectricgenerators in the first and second thermoelectric generator units. Inthe medium path, a further fluid may flow in the same direction throughthe respective flow paths of the plurality of tubular thermoelectricgenerators.

In one embodiment, the buffer vessel contains a baffle structuretherein. The structure may be shaped to change the flow direction of thefurther fluid flowing into the buffer vessel through the respective flowpaths of the plurality of tubular thermoelectric generators, such that aportion of the further fluid flowing around a cross-sectional center ofthe buffer vessel goes outward from the cross-sectional center of thebuffer vessel.

Alternatively, The structure may be shaped to change the flow directionof the further fluid flowing into the buffer vessel through therespective flow paths of the plurality of tubular thermoelectricgenerators, such that a portion of the further fluid flowing around aninner periphery of the buffer vessel goes toward a cross-sectionalcenter of the buffer vessel.

A method of producing a thermoelectric generator system according to thepresent disclosure includes: providing the tubular thermoelectricgenerators described above; inserting the tubular thermoelectricgenerators into a plurality of openings of first and second containerswith the configuration described above so that the tubularthermoelectric generators are held inside the first and secondcontainers; electrically connecting the tubular thermoelectricgenerators together via a plurality of electrically conductive members;and arranging a buffer vessel between the first and second containers.The buffer vessel has a first opening communicating with the respectiveflow paths of the tubular thermoelectric generators housed in the firstcontainer and a second opening communicating with the respective flowpaths of the tubular thermoelectric generators housed in the secondcontainer.

A method of generating electric power according to the presentdisclosure includes: introducing a first medium through fluid inlet andoutlet ports of the container of each said thermoelectric generator unitof the thermoelectric generator system described above and bringing thefirst medium into contact with the outer peripheral surface of eachtubular thermoelectric generator; introducing a second medium having adifferent temperature from the first medium into the flow paths of therespective tubular thermoelectric generators; and extracting electricpower generated by the tubular thermoelectric generators through theelectrically conductive members.

A thermoelectric generator unit according to the present disclosure maybe used by itself without being connected with other units via thebuffer vessel. A thermoelectric generator unit according to the presentdisclosure includes a plurality of tubular thermoelectric generators,each of which has an outer peripheral surface, an inner peripheralsurface and a flow path defined by the inner peripheral surface, and isconfigured to generate electromotive force in an axial direction of eachtubular thermoelectric generator based on a difference in temperaturebetween the inner and outer peripheral surfaces. Typically, thosetubular thermoelectric generators are electrically connected together inseries via a plurality of plate electrically conductive members. Thoseelectrically conductive members may be located inside or outside of thecontainer that surrounds the tubular thermoelectric generators as longas the plate electrically conductive members are insulated from the heattransfer medium.

A thermoelectric generator system according to the present disclosuremay be used as a power generator which utilizes the heat of an exhaustgas exhausted from a car or a factory, for example.

While the present invention has been described with respect to exemplaryembodiments thereof, it will be apparent to those skilled in the artthat the disclosed invention may be modified in numerous ways and mayassume many embodiments other than those specifically described above.Accordingly, it is intended by the appended claims to cover allmodifications of the invention that fall within the true spirit andscope of the invention.

What is claimed is:
 1. A thermoelectric generator system comprising aplurality of thermoelectric generator units including first and secondthermoelectric generator units, each of which includes a plurality oftubular thermoelectric generators, wherein each of the plurality oftubular thermoelectric generators has an outer peripheral surface, aninner peripheral surface and a flow path defined by the inner peripheralsurface, and generates electromotive force in an axial direction of eachsaid tubular thermoelectric generator based on a difference intemperature between the inner and outer peripheral surfaces, each of thefirst and second thermoelectric generator units further includes: acontainer housing the plurality of tubular thermoelectric generatorsinside, the container having fluid inlet and outlet ports through whicha fluid flows inside the container, and a plurality of openings intowhich the respective tubular thermoelectric generators are inserted; afluid conduit connected between the fluid outlet port of the containerof the first thermoelectric generator unit and the fluid inlet port ofthe container of the second thermoelectric generator unit, through whichfluid from the first thermoelectric generator unit is communicated intothe second thermoelectric generator unit, wherein the fluid conduitdefines a first medium path communicating with the fluid inlet andoutlet ports of the container in the first thermoelectric generator unitand the fluid inlet and outlet ports of the container in the secondthermoelectric generator unit; and a plurality of electricallyconductive members providing electrical interconnection for theplurality of tubular thermoelectric generators, and the thermoelectricgenerator system further includes a buffer vessel which is arrangedbetween the first and second thermoelectric generator units, the buffervessel having a first opening communicating with the respective flowpaths of the plurality of tubular thermoelectric generators in the firstthermoelectric generator unit and a second opening communicating withthe respective flow paths of the plurality of tubular thermoelectricgenerators in the second thermoelectric generator unit, wherein thebuffer vessel defines a second medium path between the respective flowpaths of the plurality of tubular thermoelectric generators in the firstthermoelectric generator unit and the respective flow paths of theplurality of tubular thermoelectric generators in the secondthermoelectric generator unit, wherein in the second medium path, fluidflows downstream from inside the plurality of tubular thermoelectricgenerators in the second thermoelectric generator unit through thebuffer vessel and to inside the plurality of tubular thermoelectricgenerators in the first thermoelectric generator unit, and wherein inthe first medium path, fluid flows downstream from an area inside thecontainer of the first thermoelectric generator unit that is outside theplurality of tubular thermoelectric generators in the firstthermoelectric generator unit, through the fluid conduit outside of thecontainer of the first thermoelectric generator unit, and to an areathat is inside the container of the second thermoelectric generator unitand outside the plurality of tubular thermoelectric generators in thesecond thermoelectric generator unit.
 2. The thermoelectric generatorsystem of claim 1, wherein the buffer vessel contains a baffle structuretherein.
 3. The thermoelectric generator system of claim 2, wherein thebaffle structure is shaped to change at least partially a flow directionof the fluid flowing in the second medium path into the buffer vessel.4. The thermoelectric generator system of claim 3, wherein the bafflestructure includes at least one baffle plate.
 5. The thermoelectricgenerator system of claim 3, wherein the baffle structure has a movableportion.
 6. The thermoelectric generator system of claim 3, wherein thebaffle structure is shaped to change the flow direction of the fluidflowing in the second medium path around a cross-sectional center of thebuffer vessel.
 7. The thermoelectric generator system of claim 3,wherein the baffle structure is shaped to radially expand gradually inthe flow direction of the fluid flowing in the second medium path. 8.The thermoelectric generator system of claim 3, wherein a gap is leftbetween an inner wall of the buffer vessel and an outer edge of thebaffle structure.
 9. The thermoelectric generator system of claim 3,wherein the baffle structure is shaped to change the flow direction ofthe fluid flowing in the second medium path around an inner periphery ofthe buffer vessel so that the fluid flowing in the second medium pathflows toward a cross-sectional center of the buffer vessel.
 10. Thethermoelectric generator system of claim 3, wherein the baffle structureis a projection which is provided on an inner wall of the buffer vesselso as to project toward a cross-sectional center of the buffer vessel.11. The thermoelectric generator system of claim 1, wherein thecontainer includes: a shell surrounding the plurality of tubularthermoelectric generators; and a pair of plates, each of which is fixedto the shell and at least one of which has a plurality of openings andchannels, each channel housing one of the plurality of electricallyconductive members, wherein respective ends of the tubularthermoelectric generators are inserted into the plurality of openings ofthe plates, and at least one of the channels has an interconnectionwhich connects at least two of the plurality of openings together. 12.The thermoelectric generator system of claim 1, wherein the plurality ofelectrically conductive members connect the plurality of tubularthermoelectric generators electrically in series together.
 13. Thethermoelectric generator system of claim 12, further comprising: anelectric circuit electrically connected to the plurality of tubularthermoelectric generators via at least one of the plurality ofelectrically conductive members.
 14. The thermoelectric generator systemof claim 12, wherein the first and second thermoelectric generator unitsare electrically connected in series together.
 15. A thermoelectricgenerator system comprising a plurality of thermoelectric generatorunits including first and second thermoelectric generator units, each ofwhich includes a plurality of tubular thermoelectric generators, whereineach of the plurality of tubular thermoelectric generators has an outerperipheral surface, an inner peripheral surface and a flow path definedby the inner peripheral surface, and generates electromotive force in anaxial direction of each said tubular thermoelectric generator based on adifference in temperature between the inner and outer peripheralsurfaces, each of the first and second thermoelectric generator unitsfurther includes: a container housing the plurality of tubularthermoelectric generators inside, the container having fluid inlet andoutlet ports through which a fluid flows inside the container, and aplurality of openings into which the respective tubular thermoelectricgenerators are inserted; a fluid conduit connected between the fluidoutlet port of the container of the first thermoelectric generator unitand the fluid inlet port of the container of the second thermoelectricgenerator unit, through which fluid from the first thermoelectricgenerator unit is communicated into the second thermoelectric generatorunit, wherein the fluid conduit defines a first medium pathcommunicating with the fluid inlet and outlet ports of the container inthe first thermoelectric generator unit and the fluid inlet and outletports of the container in the second thermoelectric generator unit; anda plurality of electrically conductive members providing electricalinterconnection for the plurality of tubular thermoelectric generatorsin series, the first and second thermoelectric generator units areelectrically connected in series together, the thermoelectric generatorsystem further includes a buffer vessel which is arranged between thefirst and second thermoelectric generator units, the buffer vesselhaving a first opening communicating with the respective flow paths ofthe plurality of tubular thermoelectric generators in the firstthermoelectric generator unit and a second opening communicating withthe respective flow paths of the plurality of tubular thermoelectricgenerators in the second thermoelectric generator unit, wherein thebuffer vessel defines a second medium path between the respective flowpaths of the plurality of tubular thermoelectric generators in the firstthermoelectric generator unit and the respective flow paths of theplurality of tubular thermoelectric generators in the secondthermoelectric generator unit, wherein in the second medium path, fluidflows downstream from inside the plurality of tubular thermoelectricgenerators in the second thermoelectric generator unit through thebuffer vessel and to inside the plurality of tubular thermoelectricgenerators in the first thermoelectric generator unit, and wherein inthe first medium path, fluid flows downstream from an area inside thecontainer of the first thermoelectric generator unit that is outside theplurality of tubular thermoelectric generators in the firstthermoelectric generator unit, through the fluid conduit outside of thecontainer of the first thermoelectric generator unit, and to an areathat is inside the container of the second thermoelectric generator unitand outside the plurality of tubular thermoelectric generators in thesecond thermoelectric generator unit.
 16. The thermoelectric generatorsystem of claim 15, wherein the buffer vessel contains a bafflestructure therein, the structure being shaped to change a flow directionof the fluid flowing in the second medium path into the buffer vesselthrough the respective flow paths of the plurality of tubularthermoelectric generators in the second thermoelectric generator unit,such that a portion of the fluid flowing in the second medium patharound a cross-sectional center of the buffer vessel flows outward fromthe cross-sectional center of the buffer vessel.
 17. The thermoelectricgenerator system of claim 15, wherein the buffer vessel contains abaffle structure therein, the structure being shaped to change a flowdirection of the fluid flowing in the second medium path into the buffervessel through the respective flow paths of the plurality of tubularthermoelectric generators in the second thermoelectric generator unit,such that a portion of the fluid flowing in the second medium patharound an inner periphery of the buffer vessel flows toward across-sectional center of the buffer vessel.